diff --git a/.github/workflows/main_ci.yml b/.github/workflows/main_ci.yml
index 961fc81f9..de0984617 100644
--- a/.github/workflows/main_ci.yml
+++ b/.github/workflows/main_ci.yml
@@ -22,6 +22,13 @@ jobs:
         platform: [ubuntu-latest,
                    macos-latest]
         python-version: ["3.6", "3.7", "3.8", "3.9", "3.10", "3.11"]
+        # see gh-851
+        exclude:
+          - platform: ubuntu-latest
+            python-version: "3.10"
+        include:
+          - platform: ubuntu-22.04
+            python-version: "3.10"
     runs-on: ${{ matrix.platform }}
     steps:
       - uses: actions/checkout@v3
diff --git a/darshan-runtime/lib/darshan-core.c b/darshan-runtime/lib/darshan-core.c
index c0f02f470..337a4d71e 100644
--- a/darshan-runtime/lib/darshan-core.c
+++ b/darshan-runtime/lib/darshan-core.c
@@ -151,6 +151,12 @@ static int darshan_deflate_buffer(
 static void darshan_core_cleanup(
     struct darshan_core_runtime* core);
 static void darshan_core_fork_child_cb(void);
+static void darshan_core_reduce_min_time(
+    void* in_time_v, void* inout_time_v,
+    int *len, MPI_Datatype *datatype);
+static void darshan_core_reduce_max_time(
+    void* in_time_v, void* inout_time_v,
+    int *len, MPI_Datatype *datatype);
 
 #define DARSHAN_WARN(__err_str, ...) do { \
     darshan_core_fprintf(stderr, "darshan_library_warning: " \
@@ -197,6 +203,7 @@ void darshan_core_initialize(int argc, char **argv)
     int jobid;
     int ret;
     int i;
+    struct timespec start_ts;
 
     /* setup darshan runtime if darshan is enabled and hasn't been initialized already */
     if (__darshan_core != NULL || getenv("DARSHAN_DISABLE"))
@@ -309,7 +316,9 @@ void darshan_core_initialize(int argc, char **argv)
 
         /* set known job-level metadata fields for the log file */
         init_core->log_job_p->uid = getuid();
-        init_core->log_job_p->start_time = time(NULL);
+        clock_gettime(CLOCK_REALTIME, &start_ts);
+        init_core->log_job_p->start_time_sec = (int64_t)start_ts.tv_sec;
+        init_core->log_job_p->start_time_nsec = (int64_t)start_ts.tv_nsec;
         init_core->log_job_p->nprocs = nprocs;
         init_core->log_job_p->jobid = (int64_t)jobid;
 
@@ -390,6 +399,7 @@ void darshan_core_shutdown(int write_log)
 {
     struct darshan_core_runtime *final_core;
     double start_log_time;
+    struct timespec end_ts;
     int internal_timing_flag;
     double open1 = 0, open2 = 0;
     double job1 = 0, job2 = 0;
@@ -408,6 +418,8 @@ void darshan_core_shutdown(int write_log)
     int i;
     int ret;
 #ifdef HAVE_MPI
+    MPI_Datatype ts_type;
+    MPI_Op ts_max_op, ts_min_op;
     darshan_record_id *shared_recs = NULL;
     darshan_record_id *mod_shared_recs = NULL;
     int shared_rec_cnt = 0;
@@ -442,7 +454,9 @@ void darshan_core_shutdown(int write_log)
         PMPI_Barrier(final_core->mpi_comm);
 #endif
     start_log_time = darshan_core_wtime_absolute();
-    final_core->log_job_p->end_time = time(NULL);
+    clock_gettime(CLOCK_REALTIME, &end_ts);
+    final_core->log_job_p->end_time_sec = (int64_t)end_ts.tv_sec;
+    final_core->log_job_p->end_time_nsec = (int64_t)end_ts.tv_nsec;
 
     internal_timing_flag = final_core->config.internal_timing_flag;
 
@@ -476,22 +490,30 @@ void darshan_core_shutdown(int write_log)
             MPI_INT, MPI_SUM, final_core->mpi_comm);
 
         /* reduce to report first start and last end time across all ranks at rank 0 */
+        /* NOTE: custom MPI max/min reduction operators required for sec/nsec time tuples */
+        PMPI_Type_contiguous(2, MPI_INT64_T, &ts_type);
+        PMPI_Type_commit(&ts_type);
+        PMPI_Op_create(darshan_core_reduce_min_time, 1, &ts_min_op);
+        PMPI_Op_create(darshan_core_reduce_max_time, 1, &ts_max_op);
         if(my_rank == 0)
         {
-            PMPI_Reduce(MPI_IN_PLACE, &final_core->log_job_p->start_time,
-                1, MPI_INT64_T, MPI_MIN, 0, final_core->mpi_comm);
-            PMPI_Reduce(MPI_IN_PLACE, &final_core->log_job_p->end_time,
-                1, MPI_INT64_T, MPI_MAX, 0, final_core->mpi_comm);
+            PMPI_Reduce(MPI_IN_PLACE, &final_core->log_job_p->start_time_sec,
+                1, ts_type, ts_min_op, 0, final_core->mpi_comm);
+            PMPI_Reduce(MPI_IN_PLACE, &final_core->log_job_p->end_time_sec,
+                1, ts_type, ts_max_op, 0, final_core->mpi_comm);
         }
         else
         {
-            PMPI_Reduce(&final_core->log_job_p->start_time,
-                &final_core->log_job_p->start_time,
-                1, MPI_INT64_T, MPI_MIN, 0, final_core->mpi_comm);
-            PMPI_Reduce(&final_core->log_job_p->end_time,
-                &final_core->log_job_p->end_time,
-                1, MPI_INT64_T, MPI_MAX, 0, final_core->mpi_comm);
+            PMPI_Reduce(&final_core->log_job_p->start_time_sec,
+                &final_core->log_job_p->start_time_sec,
+                1, ts_type, ts_min_op, 0, final_core->mpi_comm);
+            PMPI_Reduce(&final_core->log_job_p->end_time_sec,
+                &final_core->log_job_p->end_time_sec,
+                1, ts_type, ts_max_op, 0, final_core->mpi_comm);
         }
+        PMPI_Type_free(&ts_type);
+        PMPI_Op_free(&ts_min_op);
+        PMPI_Op_free(&ts_max_op);
 
         /* get a list of records which are shared across all processes */
         darshan_get_shared_records(final_core, &shared_recs, &shared_rec_cnt);
@@ -1486,7 +1508,6 @@ static void darshan_get_logfile_name(
 
     jobid = core->log_job_p->jobid;
     pid = core->pid;
-    start_time = core->log_job_p->start_time;
 
     /* first, check if user specifies a complete logpath to use */
     user_logfile_name = getenv("DARSHAN_LOGFILE");
@@ -1514,6 +1535,7 @@ static void darshan_get_logfile_name(
         logmod = darshan_hash((void*)hname,strlen(hname),hlevel);
 
         /* use human readable start time format in log filename */
+        start_time = (time_t)core->log_job_p->start_time_sec;
         start_tm = localtime(&start_time);
 
         if(core->config.log_path_byenv)
@@ -2262,6 +2284,84 @@ static int darshan_core_name_is_excluded(const char *name, darshan_module_id mod
     return(0);
 }
 
+#ifdef HAVE_MPI
+static void darshan_core_reduce_min_time(void* in_time_v, void* inout_time_v,
+    int *len, MPI_Datatype *datatype)
+{
+    int64_t tmp_sec, tmp_nsec;
+    int64_t *in_sec = in_time_v;
+    int64_t *in_nsec = in_sec+1;
+    int64_t *inout_sec = inout_time_v;
+    int64_t *inout_nsec = inout_sec+1;
+    int i;
+
+    for(i=0; i<*len; i++)
+    {
+        /* min */
+        if((*in_sec < *inout_sec) ||
+            ((*in_sec == *inout_sec) &&
+             (*in_nsec < *inout_nsec)))
+        {
+            tmp_sec = *in_sec;
+            tmp_nsec = *in_nsec;
+        }
+        else
+        {
+            tmp_sec = *inout_sec;
+            tmp_nsec = *inout_nsec;
+        }
+
+        /* update pointers */
+        *inout_sec = tmp_sec;
+        *inout_nsec = tmp_nsec;
+        inout_sec+=2;
+        inout_nsec+=2;
+        in_sec+=2;
+        in_nsec+=2;
+    }
+
+    return;
+}
+
+static void darshan_core_reduce_max_time(void* in_time_v, void* inout_time_v,
+    int *len, MPI_Datatype *datatype)
+{
+    int64_t tmp_sec, tmp_nsec;
+    int64_t *in_sec = in_time_v;
+    int64_t *in_nsec = in_sec+1;
+    int64_t *inout_sec = inout_time_v;
+    int64_t *inout_nsec = inout_sec+1;
+    int i;
+
+    for(i=0; i<*len; i++)
+    {
+        /* max */
+        if((*in_sec > *inout_sec) ||
+            ((*in_sec == *inout_sec) &&
+             (*in_nsec > *inout_nsec)))
+        {
+            tmp_sec = *in_sec;
+            tmp_nsec = *in_nsec;
+        }
+        else
+        {
+            tmp_sec = *inout_sec;
+            tmp_nsec = *inout_nsec;
+        }
+
+        /* update pointers */
+        *inout_sec = tmp_sec;
+        *inout_nsec = tmp_nsec;
+        inout_sec+=2;
+        inout_nsec+=2;
+        in_sec+=2;
+        in_nsec+=2;
+    }
+
+    return;
+}
+#endif
+
 /* crude benchmarking hook into darshan-core to benchmark Darshan
  * shutdown overhead using a variety of application I/O workloads
  */
diff --git a/darshan-util/darshan-analyzer.c b/darshan-util/darshan-analyzer.c
index 293b7ef7c..f57ad7179 100644
--- a/darshan-util/darshan-analyzer.c
+++ b/darshan-util/darshan-analyzer.c
@@ -97,11 +97,7 @@ int process_log(const char *fname, double *io_ratio, int *used_mpio, int *used_p
     if (file->mod_map[DARSHAN_PNETCDF_FILE_MOD].len > 0 || file->mod_map[DARSHAN_PNETCDF_VAR_MOD].len > 0)
         *used_pnet += 1;
 
-    total_job_time = (double)job.end_time - (double)job.start_time;
-    if (total_job_time < 1.0)
-    {
-        total_job_time = 1.0;
-    }
+    darshan_log_get_job_runtime(file, job, &total_job_time);
 
     if (f_count > 0)
     {
diff --git a/darshan-util/darshan-diff.c b/darshan-util/darshan-diff.c
index e92f855d1..8e89c8d9e 100644
--- a/darshan-util/darshan-diff.c
+++ b/darshan-util/darshan-diff.c
@@ -133,16 +133,16 @@ int main(int argc, char *argv[])
 
     if (job1.uid != job2.uid)
         print_int64_diff("# uid:", job1.uid, job2.uid);
-    if (job1.start_time != job2.start_time)
-        print_int64_diff("# start_time:", job1.start_time, job2.start_time);
-    if (job1.end_time != job2.end_time)
-        print_int64_diff("# end_time:", job1.end_time, job2.end_time);
+    if (job1.start_time_sec != job2.start_time_sec)
+        print_int64_diff("# start_time:", job1.start_time_sec, job2.start_time_sec);
+    if (job1.end_time_sec != job2.end_time_sec)
+        print_int64_diff("# end_time:", job1.end_time_sec, job2.end_time_sec);
     if (job1.nprocs != job2.nprocs)
         print_int64_diff("# nprocs:", job1.nprocs, job2.nprocs);
-    if ((job1.end_time-job1.start_time) != (job2.end_time - job2.start_time))
+    if ((job1.end_time_sec-job1.start_time_sec) != (job2.end_time_sec-job2.start_time_sec))
         print_int64_diff("# run time:",
-                (int64_t)(job1.end_time - job1.start_time + 1),
-                (int64_t)(job2.end_time - job2.start_time + 1));
+                (int64_t)(job1.end_time_sec - job1.start_time_sec + 1),
+                (int64_t)(job2.end_time_sec - job2.start_time_sec + 1));
 
     /* get hash of record ids to file names for each log */
     ret = darshan_log_get_namehash(file1, &name_hash1);
diff --git a/darshan-util/darshan-dxt-parser.c b/darshan-util/darshan-dxt-parser.c
index 69b3db7e8..23007b92c 100644
--- a/darshan-util/darshan-dxt-parser.c
+++ b/darshan-util/darshan-dxt-parser.c
@@ -43,7 +43,7 @@ int main(int argc, char **argv)
     int mount_count;
     struct darshan_mnt_info *mnt_data_array;
     time_t tmp_time = 0;
-    int64_t run_time = 0;
+    double run_time;
     char *token;
     char *save;
     char buffer[DARSHAN_JOB_METADATA_LEN];
@@ -107,17 +107,16 @@ int main(int argc, char **argv)
     printf("# exe: %s\n", tmp_string);
     printf("# uid: %" PRId64 "\n", job.uid);
     printf("# jobid: %" PRId64 "\n", job.jobid);
-    printf("# start_time: %" PRId64 "\n", job.start_time);
-    tmp_time += job.start_time;
+    printf("# start_time: %" PRId64 "\n", job.start_time_sec);
+    tmp_time += job.start_time_sec;
     printf("# start_time_asci: %s", ctime(&tmp_time));
-    printf("# end_time: %" PRId64 "\n", job.end_time);
+    printf("# end_time: %" PRId64 "\n", job.end_time_sec);
     tmp_time = 0;
-    tmp_time += job.end_time;
+    tmp_time += job.end_time_sec;
     printf("# end_time_asci: %s", ctime(&tmp_time));
     printf("# nprocs: %" PRId64 "\n", job.nprocs);
-    if (job.end_time >= job.start_time)
-        run_time = job.end_time - job.start_time + 1;
-    printf("# run time: %" PRId64 "\n", run_time);
+    darshan_log_get_job_runtime(fd, job, &run_time);
+    printf("# run time: %.4lf\n", run_time);
     for (token = strtok_r(job.metadata, "\n", &save);
         token != NULL;
         token = strtok_r(NULL, "\n", &save))
diff --git a/darshan-util/darshan-logutils.c b/darshan-util/darshan-logutils.c
index d1379a5b4..613d49f5d 100644
--- a/darshan-util/darshan-logutils.c
+++ b/darshan-util/darshan-logutils.c
@@ -270,8 +270,11 @@ darshan_fd darshan_log_create(const char *name, enum darshan_comp_type comp_type
 int darshan_log_get_job(darshan_fd fd, struct darshan_job *job)
 {
     struct darshan_fd_int_state *state;
+    int log_ver_maj, log_ver_min;
     char job_buf[DARSHAN_JOB_RECORD_SIZE] = {0};
     int job_buf_sz = DARSHAN_JOB_RECORD_SIZE;
+    char *trailing_data;
+    int trailing_data_size;
     int ret;
 
     if(!fd)
@@ -283,6 +286,14 @@ int darshan_log_get_job(darshan_fd fd, struct darshan_job *job)
     assert(state);
     assert(fd->job_map.len > 0 && fd->job_map.off > 0);
 
+    /* get major/minor version numbers */
+    ret = darshan_log_get_format_version(fd->version, &log_ver_maj, &log_ver_min);
+    if(ret < 0)
+    {
+        fprintf(stderr, "Error: unable to parse log file format version.\n");
+        return(-1);
+    }
+
     /* read the compressed job data from the log file */
     ret = darshan_log_dzread(fd, DARSHAN_JOB_REGION_ID, job_buf, job_buf_sz);
     if(ret <= (int)sizeof(*job))
@@ -291,24 +302,54 @@ int darshan_log_get_job(darshan_fd fd, struct darshan_job *job)
         return(-1);
     }
 
-    memcpy(job, job_buf, sizeof(*job));
+    /* NOTE: job definition changed to include start/end time nsecs in ver 3.41 */
+    if(((log_ver_maj == 3) && (log_ver_min >= 41)) || (log_ver_maj > 3))
+    {
+        memcpy(job, job_buf, sizeof(*job));
+        trailing_data = &job_buf[sizeof(*job)];
+        trailing_data_size = DARSHAN_EXE_LEN+1;
+    }
+    else
+    {
+        /* backwards compatibility with prior of Darshan job struct,
+         * which does not have fields for start_time_nsec or
+         * end_time_nsec
+         */
+        int64_t *tmp_ptr = (int64_t *)job_buf;
+        job->uid = *(tmp_ptr++);
+        job->start_time_sec = *(tmp_ptr++);
+        job->start_time_nsec = 0;
+        job->end_time_sec = *(tmp_ptr++);
+        job->end_time_nsec = 0;
+        job->nprocs = *(tmp_ptr++);
+        job->jobid = *(tmp_ptr++);
+        memcpy(job->metadata, tmp_ptr, DARSHAN_JOB_METADATA_LEN);
+        trailing_data = (char *)tmp_ptr + DARSHAN_JOB_METADATA_LEN;
+        trailing_data_size = DARSHAN_EXE_LEN+1+(2*sizeof(int64_t));
+    }
 
     if(fd->swap_flag)
     {
         /* swap bytes if necessary */
         DARSHAN_BSWAP64(&job->uid);
-        DARSHAN_BSWAP64(&job->start_time);
-        DARSHAN_BSWAP64(&job->end_time);
+        DARSHAN_BSWAP64(&job->start_time_sec);
+        DARSHAN_BSWAP64(&job->end_time_sec);
+        /* don't byte swap fields explicitly set during up-conversion */
+        if(((log_ver_maj == 3) && (log_ver_min >= 41)) || (log_ver_maj > 3))
+        {
+            DARSHAN_BSWAP64(&job->start_time_nsec);
+            DARSHAN_BSWAP64(&job->end_time_nsec);
+        }
         DARSHAN_BSWAP64(&job->nprocs);
         DARSHAN_BSWAP64(&job->jobid);
     }
 
     /* save trailing exe & mount information, so it can be retrieved later */
     if(!(state->exe_mnt_data))
-        state->exe_mnt_data = malloc(DARSHAN_EXE_LEN+1);
+        state->exe_mnt_data = malloc(trailing_data_size);
     if(!(state->exe_mnt_data))
         return(-1);
-    memcpy(state->exe_mnt_data, &job_buf[sizeof(*job)], DARSHAN_EXE_LEN+1);
+    memcpy(state->exe_mnt_data, trailing_data, trailing_data_size);
 
     return(0);
 }
@@ -893,6 +934,29 @@ char *darshan_log_get_lib_version(void)
     return darshan_util_lib_ver;
 }
 
+int darshan_log_get_job_runtime(darshan_fd fd, struct darshan_job job, double *runtime)
+{
+    int log_ver_maj, log_ver_min;
+    int ret;
+    *runtime = 0;
+
+    /* get major/minor version numbers */
+    ret = darshan_log_get_format_version(fd->version, &log_ver_maj, &log_ver_min);
+    if(ret < 0)
+    {
+        fprintf(stderr, "Error: unable to parse log file format version.\n");
+        return(-1);
+    }
+
+    if(((log_ver_maj == 3) && (log_ver_min >= 41)) || (log_ver_maj > 3))
+        *runtime = (double)((job.end_time_sec + (job.end_time_nsec / 1e9)) -
+                    (job.start_time_sec + (job.start_time_nsec / 1e9)));
+    else
+        *runtime = (double)(job.end_time_sec - job.start_time_sec + 1);
+
+    return(0);
+}
+
 /********************************************************
  *             internal helper functions                *
  ********************************************************/
diff --git a/darshan-util/darshan-logutils.h b/darshan-util/darshan-logutils.h
index f30976624..2cdbba7e3 100644
--- a/darshan-util/darshan-logutils.h
+++ b/darshan-util/darshan-logutils.h
@@ -211,6 +211,7 @@ int darshan_log_put_mod(darshan_fd fd, darshan_module_id mod_id,
 void darshan_log_close(darshan_fd file);
 void darshan_log_print_version_warnings(const char *version_string);
 char *darshan_log_get_lib_version(void);
+int darshan_log_get_job_runtime(darshan_fd fd, struct darshan_job job, double *runtime);
 void darshan_log_get_modules(darshan_fd fd, struct darshan_mod_info **mods,
     int* count);
 void darshan_log_get_name_records(darshan_fd fd,
diff --git a/darshan-util/darshan-merge.c b/darshan-util/darshan-merge.c
index e7a41016c..ecc76d9b1 100644
--- a/darshan-util/darshan-merge.c
+++ b/darshan-util/darshan-merge.c
@@ -286,10 +286,20 @@ int main(int argc, char *argv[])
         else
         {
             /* potentially update job timestamps using remaining logs */
-            if(in_job.start_time < merge_job.start_time)
-                merge_job.start_time = in_job.start_time;
-            if(in_job.end_time > merge_job.end_time)
-                merge_job.end_time = in_job.end_time;
+            if((in_job.start_time_sec < merge_job.start_time_sec) ||
+               ((in_job.start_time_sec == merge_job.start_time_sec) &&
+                (in_job.start_time_nsec < merge_job.start_time_nsec)))
+            {
+                merge_job.start_time_sec = in_job.start_time_sec;
+                merge_job.start_time_nsec = in_job.start_time_nsec;
+            }
+            if((in_job.end_time_sec > merge_job.end_time_sec) ||
+               ((in_job.end_time_sec == merge_job.end_time_sec) &&
+                (in_job.end_time_nsec > merge_job.end_time_nsec)))
+            {
+                merge_job.end_time_sec = in_job.end_time_sec;
+                merge_job.end_time_nsec = in_job.end_time_nsec;
+            }
         }
 
         /* read the hash of ids->names for the input log */
@@ -329,7 +339,10 @@ int main(int argc, char *argv[])
 
     /* if a job end time was passed in, apply it to the output job */
     if(job_end_time > 0)
-        merge_job.end_time = job_end_time;
+    {
+        merge_job.end_time_sec = job_end_time;
+        merge_job.end_time_nsec = 0; /* no nsec precision for manually specified end */
+    }
 
     /* create the output "merged" log */
     merge_fd = darshan_log_create(outlog_path, DARSHAN_ZLIB_COMP, 1);
diff --git a/darshan-util/darshan-parser.c b/darshan-util/darshan-parser.c
index f2c847dbf..83c97eefc 100644
--- a/darshan-util/darshan-parser.c
+++ b/darshan-util/darshan-parser.c
@@ -140,7 +140,7 @@ int main(int argc, char **argv)
     int mount_count;
     struct darshan_mnt_info *mnt_data_array;
     time_t tmp_time = 0;
-    int64_t run_time = 0;
+    double run_time;
     char *token;
     char *save;
     char buffer[DARSHAN_JOB_METADATA_LEN];
@@ -206,17 +206,16 @@ int main(int argc, char **argv)
     printf("# exe: %s\n", tmp_string);
     printf("# uid: %" PRId64 "\n", job.uid);
     printf("# jobid: %" PRId64 "\n", job.jobid);
-    printf("# start_time: %" PRId64 "\n", job.start_time);
-    tmp_time += job.start_time;
+    printf("# start_time: %" PRId64 "\n", job.start_time_sec);
+    tmp_time += job.start_time_sec;
     printf("# start_time_asci: %s", ctime(&tmp_time));
-    printf("# end_time: %" PRId64 "\n", job.end_time);
+    printf("# end_time: %" PRId64 "\n", job.end_time_sec);
     tmp_time = 0;
-    tmp_time += job.end_time;
+    tmp_time += job.end_time_sec;
     printf("# end_time_asci: %s", ctime(&tmp_time));
     printf("# nprocs: %" PRId64 "\n", job.nprocs);
-    if(job.end_time >= job.start_time)
-        run_time = job.end_time - job.start_time + 1;
-    printf("# run time: %" PRId64 "\n", run_time);
+    darshan_log_get_job_runtime(fd, job, &run_time);
+    printf("# run time: %.4lf\n", run_time);
     for(token=strtok_r(job.metadata, "\n", &save);
         token != NULL;
         token=strtok_r(NULL, "\n", &save))
diff --git a/darshan-util/pydarshan/darshan/backend/api_def_c.py b/darshan-util/pydarshan/darshan/backend/api_def_c.py
index c3ab61d08..5fce60b5e 100644
--- a/darshan-util/pydarshan/darshan/backend/api_def_c.py
+++ b/darshan-util/pydarshan/darshan/backend/api_def_c.py
@@ -10,8 +10,8 @@
 header = """/* from darshan-logutils.h */
 struct darshan_mnt_info
 {
-    char mnt_type[3031];
-    char mnt_path[3031];
+    char mnt_type[3015];
+    char mnt_path[3015];
 };
 
 struct darshan_mod_info
@@ -29,8 +29,10 @@
 struct darshan_job
 {
     int64_t uid;
-    int64_t start_time;
-    int64_t end_time;
+    int64_t start_time_sec;
+    int64_t start_time_nsec;
+    int64_t end_time_sec;
+    int64_t end_time_nsec;
     int64_t nprocs;
     int64_t jobid;
     char metadata[1024];
@@ -167,6 +169,7 @@
 void darshan_log_get_modules(void*, struct darshan_mod_info **, int*);
 int darshan_log_get_record(void*, int, void **);
 char* darshan_log_get_lib_version(void);
+int darshan_log_get_job_runtime(void *, struct darshan_job job, double *runtime);
 void darshan_free(void *);
 
 int darshan_log_get_namehash(void*, struct darshan_name_record_ref **hash);
diff --git a/darshan-util/pydarshan/darshan/backend/cffi_backend.py b/darshan-util/pydarshan/darshan/backend/cffi_backend.py
index 62c9f11b0..982fb2e86 100644
--- a/darshan-util/pydarshan/darshan/backend/cffi_backend.py
+++ b/darshan-util/pydarshan/darshan/backend/cffi_backend.py
@@ -126,11 +126,17 @@ def log_get_job(log):
     libdutil.darshan_log_get_job(log['handle'], jobrec)
 
     job['uid'] = jobrec[0].uid
-    job['start_time'] = jobrec[0].start_time
-    job['end_time'] = jobrec[0].end_time
+    job['start_time_sec'] = jobrec[0].start_time_sec
+    job['start_time_nsec'] = jobrec[0].start_time_nsec
+    job['end_time_sec'] = jobrec[0].end_time_sec
+    job['end_time_nsec'] = jobrec[0].end_time_nsec
     job['nprocs'] = jobrec[0].nprocs
     job['jobid'] = jobrec[0].jobid
 
+    runtime = ffi.new("double *")
+    libdutil.darshan_log_get_job_runtime(log['handle'], jobrec[0], runtime)
+    job['run_time'] = runtime[0]
+
     # dirty hack to get log format version -- we know it's currently stored at the
     # very beginning of the log handle structure, so we just cast the struct
     # pointer as a string...
diff --git a/darshan-util/pydarshan/darshan/cli/summary.py b/darshan-util/pydarshan/darshan/cli/summary.py
index b166c2389..7d9c0944c 100644
--- a/darshan-util/pydarshan/darshan/cli/summary.py
+++ b/darshan-util/pydarshan/darshan/cli/summary.py
@@ -178,16 +178,9 @@ def get_runtime(report: darshan.report.DarshanReport) -> str:
         runtime : the calculated executable run time.
 
         """
-        # calculate the run time
-        runtime_val = int(
-            report.metadata["job"]["end_time"] - report.metadata["job"]["start_time"]
-        )
-        if runtime_val < 1:
-            # to prevent the displayed run time from being 0 seconds
-            # label anything under 1 second as less than 1
-            runtime = "< 1"
-        else:
-            runtime = str(runtime_val)
+        # get the run time string
+        runtime_val = report.metadata["job"]["run_time"]
+        runtime = f'{runtime_val:.4f}'
         return runtime
 
     def get_header(self):
@@ -200,7 +193,7 @@ def get_header(self):
         else:
             app_name = os.path.basename(command.split()[0])
         # collect the date from the time stamp
-        date = datetime.date.fromtimestamp(self.report.metadata["job"]["start_time"])
+        date = datetime.date.fromtimestamp(self.report.metadata["job"]["start_time_sec"])
         # the header is the application name and the log date
         self.header = f"{app_name} ({date})"
 
@@ -222,9 +215,9 @@ def get_metadata_table(self):
             "Job ID": job_data["jobid"],
             "User ID": job_data["uid"],
             "# Processes": job_data["nprocs"],
-            "Runtime (s)": self.get_runtime(report=self.report),
-            "Start Time": datetime.datetime.fromtimestamp(job_data["start_time"]),
-            "End Time": datetime.datetime.fromtimestamp(job_data["end_time"]),
+            "Run time (s)": self.get_runtime(report=self.report),
+            "Start Time": datetime.datetime.fromtimestamp(job_data["start_time_sec"]),
+            "End Time": datetime.datetime.fromtimestamp(job_data["end_time_sec"]),
             "Command Line": self.get_full_command(report=self.report),
         }
         # convert the dictionary into a dataframe
diff --git a/darshan-util/pydarshan/darshan/examples/example_logs/shane_ior-HDF5_id438090-438090_11-9-41522-17417065676046418211_1.darshan b/darshan-util/pydarshan/darshan/examples/example_logs/shane_ior-HDF5_id438090-438090_11-9-41522-17417065676046418211_1.darshan
new file mode 100644
index 000000000..45f6f8d57
Binary files /dev/null and b/darshan-util/pydarshan/darshan/examples/example_logs/shane_ior-HDF5_id438090-438090_11-9-41522-17417065676046418211_1.darshan differ
diff --git a/darshan-util/pydarshan/darshan/examples/example_logs/shane_ior-HDF5_id545128-545128_9-7-60657-7307669767025130365_1.darshan b/darshan-util/pydarshan/darshan/examples/example_logs/shane_ior-HDF5_id545128-545128_9-7-60657-7307669767025130365_1.darshan
deleted file mode 100644
index 0f01b258a..000000000
Binary files a/darshan-util/pydarshan/darshan/examples/example_logs/shane_ior-HDF5_id545128-545128_9-7-60657-7307669767025130365_1.darshan and /dev/null differ
diff --git a/darshan-util/pydarshan/darshan/examples/example_logs/shane_ior-PNETCDF_id438100-438100_11-9-41525-10280033558448664385_1.darshan b/darshan-util/pydarshan/darshan/examples/example_logs/shane_ior-PNETCDF_id438100-438100_11-9-41525-10280033558448664385_1.darshan
new file mode 100644
index 000000000..67fe1bf1e
Binary files /dev/null and b/darshan-util/pydarshan/darshan/examples/example_logs/shane_ior-PNETCDF_id438100-438100_11-9-41525-10280033558448664385_1.darshan differ
diff --git a/darshan-util/pydarshan/darshan/examples/example_logs/shane_ior-PNETCDF_id864223-864223_10-27-46849-11258636277699483231_1.darshan b/darshan-util/pydarshan/darshan/examples/example_logs/shane_ior-PNETCDF_id864223-864223_10-27-46849-11258636277699483231_1.darshan
deleted file mode 100644
index 29d843987..000000000
Binary files a/darshan-util/pydarshan/darshan/examples/example_logs/shane_ior-PNETCDF_id864223-864223_10-27-46849-11258636277699483231_1.darshan and /dev/null differ
diff --git a/darshan-util/pydarshan/darshan/experimental/aggregators/create_dxttimeline.py b/darshan-util/pydarshan/darshan/experimental/aggregators/create_dxttimeline.py
index 3f4e4c8e6..92b244821 100644
--- a/darshan-util/pydarshan/darshan/experimental/aggregators/create_dxttimeline.py
+++ b/darshan-util/pydarshan/darshan/experimental/aggregators/create_dxttimeline.py
@@ -22,7 +22,7 @@ def create_dxttimeline(self, group_by='rank', mode="append"):
     items = ctx['items']
     
 
-    start_time = datetime.datetime.fromtimestamp( self.data['metadata']['job']['start_time'] )
+    start_time = datetime.datetime.fromtimestamp( self.data['metadata']['job']['start_time_sec'] )
 
 
 
diff --git a/darshan-util/pydarshan/darshan/experimental/plots/plot_dxt_heatmap.py b/darshan-util/pydarshan/darshan/experimental/plots/plot_dxt_heatmap.py
index 00c228918..464585624 100644
--- a/darshan-util/pydarshan/darshan/experimental/plots/plot_dxt_heatmap.py
+++ b/darshan-util/pydarshan/darshan/experimental/plots/plot_dxt_heatmap.py
@@ -38,10 +38,7 @@ def determine_hmap_runtime(report: darshan.DarshanReport) -> Tuple[float, float]
     or both module types are available, to achieve a common
     max displayed runtime.
 
-    In some cases, this may mean that the time value is
-    rounded up from the actual runtime.
-
-    Paramaters
+    Parameters
     ----------
 
     report: a ``darshan.DarshanReport``
@@ -49,13 +46,11 @@ def determine_hmap_runtime(report: darshan.DarshanReport) -> Tuple[float, float]
     Returns
     -------
 
-    A tuple containing `tmax`, (rounded) `runtime` floats.
+    A tuple containing `tmax`, `runtime` floats.
 
     """
-    # calculate the elapsed runtime
-    runtime = report.metadata["job"]["end_time"] - report.metadata["job"]["start_time"]
-    # ensure a minimum runtime value of 1 second
-    runtime = max(runtime, 1)
+    # get the elapsed runtime
+    runtime = report.metadata["job"]["run_time"]
     # leverage higher resolution DXT timing
     # data if available
     if ("DXT_POSIX" in report.modules or
@@ -69,10 +64,6 @@ def determine_hmap_runtime(report: darshan.DarshanReport) -> Tuple[float, float]
                 tmax_dxt = float(agg_df["end_time"].max())
                 if tmax_dxt > tmax:
                     tmax = tmax_dxt
-        # if the data max time exceeds the runtime, buffer by 1 second
-        # until our timer precision improves to prevent truncation
-        if tmax > runtime:
-            runtime += 1
     else:
         tmax = runtime
     return tmax, runtime
diff --git a/darshan-util/pydarshan/darshan/experimental/plots/plot_io_cost.py b/darshan-util/pydarshan/darshan/experimental/plots/plot_io_cost.py
index 89c23867b..9e4bdd229 100644
--- a/darshan-util/pydarshan/darshan/experimental/plots/plot_io_cost.py
+++ b/darshan-util/pydarshan/darshan/experimental/plots/plot_io_cost.py
@@ -148,12 +148,8 @@ def plot_io_cost(report: darshan.DarshanReport) -> Any:
     stacked bar graph of the average read, write, and metadata times.
 
     """
-    # calculate the run time from the report metadata
-    runtime = report.metadata["job"]["end_time"] - report.metadata["job"]["start_time"]
-    if runtime == 0:
-        # for cases where runtime is < 1, just set it
-        # to 1 like the original perl code
-        runtime = 1
+    # get the run time from the report metadata
+    runtime = report.metadata["job"]["run_time"]
     # get the I/O cost dataframe
     io_cost_df = get_io_cost_df(report=report)
     # generate a figure with 2 y axes
diff --git a/darshan-util/pydarshan/darshan/report.py b/darshan-util/pydarshan/darshan/report.py
index afdc4c683..17b0e0e3c 100644
--- a/darshan-util/pydarshan/darshan/report.py
+++ b/darshan-util/pydarshan/darshan/report.py
@@ -476,8 +476,8 @@ def read_metadata(self, read_all=False):
         self.metadata['job'] = backend.log_get_job(self.log)
         self.metadata['exe'] = backend.log_get_exe(self.log)
 
-        self.start_time = datetime.datetime.fromtimestamp(self.metadata['job']['start_time'])
-        self.end_time = datetime.datetime.fromtimestamp(self.metadata['job']['end_time'])
+        self.start_time = datetime.datetime.fromtimestamp(self.metadata['job']['start_time_sec'])
+        self.end_time = datetime.datetime.fromtimestamp(self.metadata['job']['end_time_sec'])
 
         self.data['mounts'] = backend.log_get_mounts(self.log)
         self.mounts = self.data['mounts']
@@ -991,13 +991,13 @@ def info(self, metadata=False):
         """
         print("Filename:       ", self.filename, sep="")
 
-        tdelta = self.end_time - self.start_time
-        print("Times:          ", self.start_time, " to ", self.end_time, " (Duration ", tdelta, ")", sep="")
-
         if 'exe' in self.metadata:
-            print("Executable:    ", self.metadata['exe'], sep="")
+            print("Executable:     ", self.metadata['exe'], sep="")
+
+        print("Times:          ", self.start_time, " to ", self.end_time, sep="")
 
         if 'job' in self.metadata:
+            print("Run time:       %.4f (s)" % self.metadata['job']['run_time'], sep="")
             print("Processes:      ", self.metadata['job']['nprocs'], sep="")
             print("JobID:          ", self.metadata['job']['jobid'], sep="")
             print("UID:            ", self.metadata['job']['uid'], sep="")
diff --git a/darshan-util/pydarshan/darshan/tests/test_plot_dxt_heatmap.py b/darshan-util/pydarshan/darshan/tests/test_plot_dxt_heatmap.py
index b889d3405..24e3d307b 100644
--- a/darshan-util/pydarshan/darshan/tests/test_plot_dxt_heatmap.py
+++ b/darshan-util/pydarshan/darshan/tests/test_plot_dxt_heatmap.py
@@ -41,24 +41,24 @@ def jointgrid():
             np.linspace(0.0, 348.956244, 10),
             np.around(np.linspace(0, 1.0, 10), decimals=2),
         ),
-        ("dxt.darshan", 2, np.linspace(0.0, 100.023116, 2), [0, 1468]),
+        ("dxt.darshan", 2, np.linspace(0.0, 100.091252, 2), [0, 1469]),
         (
             "dxt.darshan",
             4,
-            np.linspace(0.0, 100.023116, 4),
-            [0, 489, 978, 1468],
+            np.linspace(0.0, 100.091252, 4),
+            [0, 489, 979, 1469],
         ),
         (
             "dxt.darshan",
             6,
-            np.linspace(0.0, 100.023116, 6),
-            [0, 293, 587, 880, 1174, 1468],
+            np.linspace(0.0, 100.091252, 6),
+            [0, 293, 587, 881, 1175, 1469],
         ),
         (
             "dxt.darshan",
             10,
-            np.linspace(0.0, 100.023116, 10),
-            [0, 163, 326, 489, 652, 815, 978, 1141, 1304, 1468],
+            np.linspace(0.0, 100.091252, 10),
+            [0, 163, 326, 489, 652, 816, 979, 1142, 1305, 1469],
         ),
         ("sample-dxt-simple.darshan", 2, np.linspace(0.0, 959.403244, 2), [0.0, 1.0]),
         (
@@ -98,7 +98,7 @@ def test_set_x_axis_ticks_and_labels(
         data = [[4, 1.03378843, 1.03387713, 0], [4000, 1.04216653, 1.04231459, 0]]
         cols = ["length", "start_time", "end_time", "rank"]
         agg_df = pd.DataFrame(data=data, columns=cols)
-        runtime = 1
+        runtime = 2
 
     else:
         filepath = get_log_path(filepath)
@@ -107,12 +107,9 @@ def test_set_x_axis_ticks_and_labels(
         agg_df = heatmap_handling.get_aggregate_data(
             report=report, mod="DXT_POSIX", ops=["read", "write"]
         )
-        runtime = report.metadata["job"]["end_time"] - report.metadata["job"]["start_time"]
+        runtime = report.metadata["job"]["run_time"]
 
-    runtime = max(runtime, 1)
     tmax_dxt = float(agg_df["end_time"].max())
-    if tmax_dxt > runtime:
-        runtime += 1
 
     # the jointgrid fixture has 100 xbins
     xbins = 100
diff --git a/darshan-util/pydarshan/darshan/tests/test_plot_exp_common.py b/darshan-util/pydarshan/darshan/tests/test_plot_exp_common.py
index 3f381d1fc..96e056461 100644
--- a/darshan-util/pydarshan/darshan/tests/test_plot_exp_common.py
+++ b/darshan-util/pydarshan/darshan/tests/test_plot_exp_common.py
@@ -125,7 +125,7 @@
             'H5D Flush', 'H5F Open', 'H5F Flush'],
         ),
         (
-            "shane_ior-PNETCDF_id864223-864223_10-27-46849-11258636277699483231_1.darshan",
+            "shane_ior-PNETCDF_id438100-438100_11-9-41525-10280033558448664385_1.darshan",
             "PNETCDF_FILE",
             plot_opcounts,
             ['Var Ind Read', 'Var Ind Write', 'Var Open', 'Var Coll Read',
@@ -133,7 +133,7 @@
              'File Ind Waits', 'File Coll Waits'],
         ),
         (
-            "shane_ior-PNETCDF_id864223-864223_10-27-46849-11258636277699483231_1.darshan",
+            "shane_ior-PNETCDF_id438100-438100_11-9-41525-10280033558448664385_1.darshan",
             "PNETCDF_VAR",
             plot_opcounts,
             ['Var Ind Read', 'Var Ind Write', 'Var Open', 'Var Coll Read',
@@ -366,13 +366,13 @@ def test_xticks_and_labels(log_path, func, expected_xticklabels, mod):
             [0, 3, 3, 0, 0, 0],
         ),
         (
-            "shane_ior-PNETCDF_id864223-864223_10-27-46849-11258636277699483231_1.darshan",
+            "shane_ior-PNETCDF_id438100-438100_11-9-41525-10280033558448664385_1.darshan",
             "PNETCDF_FILE",
             plot_opcounts,
             [0, 0, 0, 0, 0, 0, 0, 8, 0, 0, 0],
         ),
         (
-            "shane_ior-PNETCDF_id864223-864223_10-27-46849-11258636277699483231_1.darshan",
+            "shane_ior-PNETCDF_id438100-438100_11-9-41525-10280033558448664385_1.darshan",
             "PNETCDF_VAR",
             plot_opcounts,
             [16, 16, 8, 0, 0, 0, 0, 8, 0, 0, 0],
diff --git a/darshan-util/pydarshan/darshan/tests/test_plot_io_cost.py b/darshan-util/pydarshan/darshan/tests/test_plot_io_cost.py
index e5f6a7598..53c22fa5d 100644
--- a/darshan-util/pydarshan/darshan/tests/test_plot_io_cost.py
+++ b/darshan-util/pydarshan/darshan/tests/test_plot_io_cost.py
@@ -42,13 +42,13 @@
             ),
         ),
         (
-            "shane_ior-PNETCDF_id864223-864223_10-27-46849-11258636277699483231_1.darshan",
+            "shane_ior-PNETCDF_id438100-438100_11-9-41525-10280033558448664385_1.darshan",
             pd.DataFrame(
                 np.array([
-                [0.000444889069, 0.006031095982, 0.000148117542],
-                [0.000467121601, 0.006095588207, 0.003371536732],
-                [0.000423729420, 0.006246685982, 0.004460096359],
-                [0.000000000000, 0.000153362751, 0.000000000000],
+                [0.000378787518, 0.002514898777, 0.000068306923],
+                [0.000397562981, 0.002540826797, 0.001559376717],
+                [0.000402510166, 0.002579867840, 0.001994967461],
+                [0.000000000000, 0.000120997429, 0.000000000000],
                 ]),
                 ["POSIX", "MPIIO", "PNETCDF", "STDIO"],
                 ["Read", "Write", "Meta"],
@@ -71,19 +71,19 @@ def test_get_io_cost_df(logname, expected_df):
         ),
         (
             "sample-badost.darshan",
-            [0.0, 779.0],
+            [0.0, 780.0],
         ),
         (
             "dxt.darshan",
-            [0.0, 1468.0],
+            [0.0, 1469.0],
         ),
         (
             "noposix.darshan",
-            [0.0, 39212.0],
+            [0.0, 39213.0],
         ),
         (
             "noposixopens.darshan",
-            [0.0, 1110.0],
+            [0.0, 1111.0],
         ),
     ],
 )
@@ -110,7 +110,7 @@ def test_plot_io_cost_ylims(logname, expected_ylims):
         ),
         (
             "sample-badost.darshan",
-            [0.0, 155.8, 311.6, 467.4, 623.2, 779.0],
+            [0, 156, 312, 468, 624, 780],
         ),
     ],
 )
diff --git a/darshan-util/pydarshan/darshan/tests/test_report.py b/darshan-util/pydarshan/darshan/tests/test_report.py
index 680cbf9cb..55617b663 100644
--- a/darshan-util/pydarshan/darshan/tests/test_report.py
+++ b/darshan-util/pydarshan/darshan/tests/test_report.py
@@ -503,8 +503,8 @@ def test_heatmap_df_invalid_operation():
 def test_pnetcdf_hdf5_match():
     # test for some equivalent (f)counters between similar
     # HDF5 and PNETCDF-enabled runs of ior
-    pnetcdf_ior_report = darshan.DarshanReport(get_log_path("shane_ior-PNETCDF_id864223-864223_10-27-46849-11258636277699483231_1.darshan"))
-    hdf5_ior_report = darshan.DarshanReport(get_log_path("shane_ior-HDF5_id545128-545128_9-7-60657-7307669767025130365_1.darshan"))
+    pnetcdf_ior_report = darshan.DarshanReport(get_log_path("shane_ior-PNETCDF_id438100-438100_11-9-41525-10280033558448664385_1.darshan"))
+    hdf5_ior_report = darshan.DarshanReport(get_log_path("shane_ior-HDF5_id438090-438090_11-9-41522-17417065676046418211_1.darshan"))
     pnetcdf_ior_report.mod_read_all_records("PNETCDF_FILE")
     pnetcdf_ior_report.mod_read_all_records("PNETCDF_VAR")
     hdf5_ior_report.mod_read_all_records("H5F")
diff --git a/darshan-util/pydarshan/darshan/tests/test_summary.py b/darshan-util/pydarshan/darshan/tests/test_summary.py
index a4fb5a791..4b4374014 100644
--- a/darshan-util/pydarshan/darshan/tests/test_summary.py
+++ b/darshan-util/pydarshan/darshan/tests/test_summary.py
@@ -282,14 +282,14 @@ def test_header_and_footer(self, log_name, expected_header):
                 "sample.darshan",
                 pd.DataFrame(
                     index=[
-                        "Job ID", "User ID", "# Processes", "Runtime (s)",
+                        "Job ID", "User ID", "# Processes", "Run time (s)",
                         "Start Time", "End Time", "Command Line",
                     ],
                     data=[
                         "4478544",
                         "69615",
                         "2048",
-                        "116",
+                        "117.0000",
                         str(datetime.fromtimestamp(1490000867)),
                         str(datetime.fromtimestamp(1490000983)),
                         (
@@ -305,14 +305,14 @@ def test_header_and_footer(self, log_name, expected_header):
                 "noposix.darshan",
                 pd.DataFrame(
                     index=[
-                        "Job ID", "User ID", "# Processes", "Runtime (s)",
+                        "Job ID", "User ID", "# Processes", "Run time (s)",
                         "Start Time", "End Time", "Command Line",
                     ],
                     data=[
                         "83017637",
                         "996599276",
                         "512",
-                        "39212",
+                        "39213.0000",
                         str(datetime.fromtimestamp(1514923055)),
                         str(datetime.fromtimestamp(1514962267)),
                         "Anonymized",
@@ -323,14 +323,14 @@ def test_header_and_footer(self, log_name, expected_header):
                 "sample-dxt-simple.darshan",
                 pd.DataFrame(
                     index=[
-                        "Job ID", "User ID", "# Processes", "Runtime (s)",
+                        "Job ID", "User ID", "# Processes", "Run time (s)",
                         "Start Time", "End Time", "Command Line",
                     ],
                     data=[
                     "4233209",
                     "28751",
                     "16",
-                    "< 1",
+                    "1.0000",
                     str(datetime.fromtimestamp(1619109091)),
                     str(datetime.fromtimestamp(1619109091)),
                     (
@@ -538,13 +538,12 @@ def test_get_full_command(self, logname, expected_cmd):
     @pytest.mark.parametrize(
         "logname, expected_runtime",
         [
-            ("sample.darshan", "116",),
-            ("noposix.darshan", "39212"),
-            ("noposixopens.darshan", "1110"),
-            ("sample-badost.darshan", "779",),
-            ("sample-goodost.darshan", "4",),
-            # special case where the calculated run time is 0
-            ("sample-dxt-simple.darshan", "< 1",),
+            ("sample.darshan", "117.0000",),
+            ("noposix.darshan", "39213.0000"),
+            ("noposixopens.darshan", "1111.0000"),
+            ("sample-badost.darshan", "780.0000",),
+            ("sample-goodost.darshan", "5.0000",),
+            ("sample-dxt-simple.darshan", "1.0000",),
         ],
     )
     def test_get_runtime(self, logname, expected_runtime):
diff --git a/include/darshan-log-format.h b/include/darshan-log-format.h
index 7b7f21c06..4fbf37b53 100644
--- a/include/darshan-log-format.h
+++ b/include/darshan-log-format.h
@@ -83,8 +83,10 @@ struct darshan_header
 struct darshan_job
 {
     int64_t uid;
-    int64_t start_time;
-    int64_t end_time;
+    int64_t start_time_sec;
+    int64_t start_time_nsec;
+    int64_t end_time_sec;
+    int64_t end_time_nsec;
     int64_t nprocs;
     int64_t jobid;
     char metadata[DARSHAN_JOB_METADATA_LEN];