diff --git a/Project.toml b/Project.toml
index 4842d66..be4727a 100644
--- a/Project.toml
+++ b/Project.toml
@@ -10,6 +10,7 @@ Dictionaries = "85a47980-9c8c-11e8-2b9f-f7ca1fa99fb4"
 DiskArrays = "3c3547ce-8d99-4f5e-a174-61eb10b00ae3"
 LibDeflate = "9255714d-24a7-4b30-8ea3-d46a97f7e13b"
 Mmap = "a63ad114-7e13-5084-954f-fe012c677804"
+PrecompileTools = "aea7be01-6a6a-4083-8856-8a6e6704d82a"
 ResumableFunctions = "c5292f4c-5179-55e1-98c5-05642aab7184"
 StaticStrings = "4db0a0c5-418a-4e1d-8806-cb305fe13294"
 
@@ -27,6 +28,7 @@ Dictionaries = "0.4"
 DiskArrays = "0.4"
 LibDeflate = "0.4.3"
 Mmap = "1"
+PrecompileTools = "1"
 ResumableFunctions = "1"
 StaticStrings = "0.2.6"
 julia = "1.10"
diff --git a/justfile b/justfile
new file mode 100644
index 0000000..f5d993d
--- /dev/null
+++ b/justfile
@@ -0,0 +1,17 @@
+perf:
+    #!/usr/bin/env -S julia --threads=auto --project=.
+    @time using CommonDataFormat
+    elx_file = "data/elb_l2_epdef_20210914_v01.cdf"
+    @time ds = CDFDataset(elx_file)
+    @time var = ds["elb_pef_hs_Epat_eflux"]
+    @time Array(var)
+    @time var2 = ds["elb_pef_hs_epa_spec"]
+    @time Array(var2)
+    @time Array(ds["elb_pef_fs_time"])
+
+snoop:
+    #!/usr/bin/env -S julia --threads=auto --project=. -i
+    using SnoopCompileCore
+    invs = @snoop_invalidations using CommonDataFormat
+    using SnoopCompile, AbstractTrees
+    trees = invalidation_trees(invs)
\ No newline at end of file
diff --git a/src/CommonDataFormat.jl b/src/CommonDataFormat.jl
index bfd45ca..450c077 100644
--- a/src/CommonDataFormat.jl
+++ b/src/CommonDataFormat.jl
@@ -10,6 +10,7 @@ using Base.Threads
 using CodecZlib: GzipDecompressor, transcode
 using LibDeflate
 using LibDeflate: GzipDecompressResult
+using PrecompileTools
 
 export CDFDataset, CDFVariable
 export Majority, CompressionType, DataType
@@ -29,5 +30,6 @@ include("vattribute.jl")
 include("dataset.jl")
 include("loading/attribute.jl")
 include("loading/variable.jl")
+include("precompile.jl")
 
-end
+end
\ No newline at end of file
diff --git a/src/epochs.jl b/src/epochs.jl
index be71466..d25d853 100644
--- a/src/epochs.jl
+++ b/src/epochs.jl
@@ -6,6 +6,7 @@
 # 3. CDF_TIME_TT2000 (TT2000 as short) is nanoseconds since J2000 with leap seconds
 
 import Base: promote_rule, -, +
+using Dates: value, toms, tons
 
 include("leap_second.jl")
 
@@ -14,6 +15,20 @@ const EPOCH_OFFSET_SECONDS = 62167219200.0  # Seconds from year 0 to Unix epoch
 
 abstract type CDFDateTime <: Dates.AbstractDateTime end
 
+struct Picosecond <: Period
+    value::Float64
+end
+
+Picosecond(ns::Nanosecond) = convert(Picosecond, ns)
+Picosecond(p::Period) = Picosecond(Nanosecond(p))
+Base.convert(::Type{Nanosecond}, x::Picosecond) = Nanosecond(round(Int64, x.value / 1.0e3))
+Base.convert(::Type{Picosecond}, x::Nanosecond) = Picosecond(x.value * 1.0e3)
+Base.convert(::Type{Picosecond}, x::Dates.FixedPeriod) = Picosecond(Nanosecond(x))
+Base.promote_rule(::Type{Picosecond}, ::Type{<:Dates.FixedPeriod}) = Picosecond
+
+Dates._units(x::Picosecond) = " picosecond" * (abs(value(x)) == 1 ? "" : "s")
+
+
 """
     Epoch
 
@@ -56,8 +71,11 @@ fillvalue(::Epoch16) = -1.0e31
 fillvalue(::TT2000) = 9999
 
 (-)(epoch::Epoch, other::Epoch) = Millisecond(round(Int64, epoch.instant - other.instant))
-(+)(tt2000::TT2000, other::Period) = TT2000(tt2000.instant.value + Dates.tons(other))
-(+)(epoch::Epoch, other::Period) = Epoch(epoch.instant + Dates.toms(other))
+(-)(epoch::Epoch16, other::Epoch16) = Picosecond((epoch.seconds - other.seconds) * 1.0e12 + epoch.picoseconds - other.picoseconds)
+(+)(tt2000::TT2000, other::Period) = TT2000(value(tt2000) + tons(other))
+(-)(tt2000::TT2000, other::Period) = TT2000(value(tt2000) - tons(other))
+(+)(epoch::Epoch, other::Period) = Epoch(value(epoch) + toms(other))
+(-)(epoch::Epoch, other::Period) = Epoch(value(epoch) - toms(other))
 
 # Conversion to DateTime
 function Dates.DateTime(epoch::Epoch)
@@ -66,8 +84,8 @@ end
 
 function Dates.DateTime(epoch::Epoch16)
     s_since_unix = epoch.seconds - EPOCH_OFFSET_SECONDS
-    total_ns = s_since_unix * 1.0e9 + epoch.picoseconds / 1000.0
-    return DateTime(1970) + Nanosecond(round(Int64, total_ns))
+    total_ms = s_since_unix * 1.0e3 + epoch.picoseconds / 1.0e9
+    return DateTime(1970) + Millisecond(round(Int64, total_ms))
 end
 
 function Dates.DateTime(epoch::TT2000)
@@ -79,10 +97,10 @@ end
 
 # Conversion from TimeType
 function Epoch16(dt::DateTime)
-    ns_since_unix = (dt - DateTime(1970, 1, 1)).value * 1_000_000  # DateTime precision is milliseconds
-    s_since_unix = ns_since_unix / 1.0e9
+    ms_since_unix = value(dt - DateTime(1970, 1, 1))
+    s_since_unix = div(ms_since_unix, 1000)
     s_total = s_since_unix + EPOCH_OFFSET_SECONDS
-    ps_component = (ns_since_unix % 1.0e9) * 1000.0  # Convert nanoseconds remainder to picoseconds
+    ps_component = rem(ms_since_unix, 1000) * 1000000000  # Convert nanoseconds remainder to picoseconds
     return Epoch16(s_total, ps_component)
 end
 
@@ -102,11 +120,12 @@ for f in (:year, :month, :day, :hour, :minute, :second, :millisecond)
     @eval Dates.$f(epoch::CDFDateTime) = Dates.$f(DateTime(epoch))
 end
 
-Dates.value(epoch::CDFDateTime) = epoch.instant
+Dates.value(epoch::Epoch) = epoch.instant
+Dates.value(epoch::Epoch16) = ComplexF64(epoch.seconds, epoch.picoseconds)
 Dates.value(epoch::TT2000) = epoch.instant.value
 
 function Base.floor(x::T, p::Union{DatePeriod, TimePeriod}) where {T <: CDFDateTime}
-    convert(T, floor(convert(DateTime, x), p))
+    return convert(T, floor(convert(DateTime, x), p))
 end
 
 function Base.show(io::IO, epoch::CDFDateTime)
@@ -117,7 +136,12 @@ function Base.show(io::IO, epoch::CDFDateTime)
         print(io, DateTime(epoch))
     end
 end
+function Base.show(io::IO, epoch::Epoch16)
+    return print(io, DateTime(epoch))
+end
+
 Base.promote_rule(::Type{<:CDFDateTime}, ::Type{Dates.DateTime}) = Dates.DateTime
 Base.convert(::Type{Dates.DateTime}, x::CDFDateTime) = Dates.DateTime(x)
-Base.bswap(x::T) where {T <: CDFDateTime} = T(Base.bswap(x.instant))
+Base.bswap(x::Epoch) = Epoch(Base.bswap(x.instant))
+Base.bswap(x::Epoch16) = Epoch16(Base.bswap(x.seconds), Base.bswap(x.picoseconds))
 Base.bswap(x::TT2000) = TT2000(Base.bswap(x.instant.value))
diff --git a/src/parsing.jl b/src/parsing.jl
index 18a159f..ac3dc8d 100644
--- a/src/parsing.jl
+++ b/src/parsing.jl
@@ -25,7 +25,7 @@ end
 end
 
 @inline function read_be_i(v::Vector{UInt8}, i, T::Base.DataType)
-    return read_be(v, i, T), i + sizeof(T)
+    return read_be(v, i, T), i + _sizeof(T)
 end
 
 @inline function read_be_i(v::Vector{UInt8}, i, n::Integer, T)
@@ -61,7 +61,7 @@ macro read_be_fields(buffer, pos, Ts...)
     for (sym, T) in zip(value_syms, types)
         Tesc = esc(T)
         push!(stmts, :(local $sym = read_be($buf, $pos_sym, $Tesc)))
-        push!(stmts, :($pos_sym += sizeof($Tesc)))
+        push!(stmts, :($pos_sym += _sizeof($Tesc)))
     end
 
     tuple_expr = Expr(:tuple, value_syms...)
@@ -83,7 +83,7 @@ end
     for (i, idx) in enumerate(indxs)
         T = fieldtype(SType, idx)
         push!(exprs, :(local $(value_syms[i]) = read_be(buffer, $pos_sym, $T)))
-        push!(exprs, :($pos_sym += sizeof($T)))
+        push!(exprs, :($pos_sym += _sizeof($T)))
     end
 
     # Return tuple of values and final position
diff --git a/src/precompile.jl b/src/precompile.jl
new file mode 100644
index 0000000..361b587
--- /dev/null
+++ b/src/precompile.jl
@@ -0,0 +1,12 @@
+precompile(Array, (CDFVariable{TT2000, 1, VDR{Int64}, CDFDataset{NoCompression, Int64}},))
+for T in (Float32, Float64), i in 1:3
+    precompile(Array, (CDFVariable{T, i, VDR{Int64}, CDFDataset{NoCompression, Int64}},))
+end
+
+PrecompileTools.@setup_workload begin
+    elx_file = joinpath(@__DIR__, "../data/elb_l2_epdef_20210914_v01.cdf")
+
+    PrecompileTools.@compile_workload begin
+        ds = CDFDataset(elx_file)
+    end
+end
diff --git a/src/types.jl b/src/types.jl
index f1d9677..b84e9a2 100644
--- a/src/types.jl
+++ b/src/types.jl
@@ -2,4 +2,6 @@ abstract type Record end
 
 abstract type ReservedField end
 struct RInt32 <: ReservedField end
-Base.sizeof(::Type{RInt32}) = sizeof(Int32)
+
+_sizeof(x) = sizeof(x)
+_sizeof(::Type{RInt32}) = sizeof(Int32)
diff --git a/test/epochs_test.jl b/test/epochs_test.jl
index 05fa243..3f525c7 100644
--- a/test/epochs_test.jl
+++ b/test/epochs_test.jl
@@ -1,25 +1,49 @@
 using Test
 using CommonDataFormat
+import CommonDataFormat as CDF
 using Dates
 
 @testset "Epochs" begin
-    @test Epoch(DateTime(0)) == Epoch(0)
+    t = Epoch(DateTime(0))
+    @test t == Epoch(0)
     @test DateTime(Epoch(DateTime(0))) == DateTime(0)
     @test Epoch(Epoch(0)) == Epoch(0)
     @test Epoch(10) - Epoch(0) == Millisecond(10)
     @test string(Epoch(-1.0e31)) == "FILLVAL"
+    @test Epoch(10) - Millisecond(10) == Epoch(0)
+    @test Epoch(0) + Second(1) == Epoch(1000)
+    @test ntoh(hton(t)) == t
     # @test Epoch16(DateTime(0)) == Epoch16(0, 0)
 end
 
 @testset "TT2000" begin
-    @test DateTime(TT2000(DateTime(2000))) == DateTime(2000)
+    t = TT2000(DateTime(2000))
+    @test DateTime(t) == DateTime(2000)
     @test TT2000(DateTime(TT2000(0))) == TT2000(0)
     @test TT2000(TT2000(0)) == TT2000(0)
     @test TT2000(10) - TT2000(0) == Nanosecond(10)
+    @test t - Day(1) == DateTime(1999, 12, 31)
     @test floor(TT2000(0), Minute(1)) == DateTime(2000, 1, 1, 11, 58)
     @test TT2000(0) + Minute(1) == TT2000(60_000_000_000)
 
     @test string(TT2000(0)) == "2000-01-01T11:58:55.816"
     @test TT2000(0) == TT2000(0) |> bswap
     @test TT2000(0) == DateTime("2000-01-01T11:58:55.816")
-end
\ No newline at end of file
+end
+
+@testset "Epoch16" begin
+    t = Epoch16(6.377810224e10, 8.97e11)
+    @test t == DateTime(2021, 1, 17, 11, 30, 40, 897)
+    @test Epoch16(DateTime(t)) == t
+    @test string(t) == "2021-01-17T11:30:40.897"
+    @test ntoh(hton(t)) == t
+    @test Epoch16(6.377810224e10, 8.97e11) - Epoch16(6.377810224e10, 0) == CDF.Picosecond(8.97e11)
+end
+
+@testset "Picosecond" begin
+    @test CDF.Picosecond(1) == CDF.Picosecond(1)
+    @test Nanosecond(CDF.Picosecond(Nanosecond(1000))) == Nanosecond(1000)
+    @test string(CDF.Picosecond(1)) == "1.0 picosecond"
+    @test CDF.Picosecond(Millisecond(1)) == CDF.Picosecond(1.0e9)
+    @test CDF.Picosecond(1.0e9) == Millisecond(1)
+end
diff --git a/test/perf_test.jl b/test/perf_test.jl
index 1df756f..c1ea314 100644
--- a/test/perf_test.jl
+++ b/test/perf_test.jl
@@ -19,8 +19,9 @@ b2= @b full_load(elx_file)  evals=2
 
 mms_file = data_path(".mms1_scm_srvy_l2_scsrvy_20190301_v2.2.0.cdf")
 ds = CDFDataset(mms_file)
-sum(ds["mms1_scm_acb_gse_scsrvy_srvy_l2"])
-sum(ds["mms1_scm_acb_gse_scsrvy_srvy_l2"][:, 100:100000]) 
+var = ds["mms1_scm_acb_gse_scsrvy_srvy_l2"]
+sum(var)
+sum(var[:, 100:100000]) 
 b30 = @b ds["mms1_scm_acb_gse_scsrvy_srvy_l2"] evals=20
 b3= @b sum(Array(ds["mms1_scm_acb_gse_scsrvy_srvy_l2"])) evals=2
 b4= @b sum(ds["mms1_scm_acb_gse_scsrvy_srvy_l2"][:, 100:100000]) evals=5
diff --git a/test/perf_test_ntoh.jl b/test/perf_test_ntoh.jl
new file mode 100644
index 0000000..5e057a0
--- /dev/null
+++ b/test/perf_test_ntoh.jl
@@ -0,0 +1,41 @@
+a = rand(3, 100000)
+
+f1(a) = map!(ntoh, a, a)
+f2(a) = a .= ntoh.(a)
+
+using Polyester
+
+function f3(a)
+    return @inbounds @simd for i in eachindex(a)
+        a[i] = ntoh(a[i])
+    end
+end
+
+function f4(a)
+    @batch for i in eachindex(a)
+        a[i] = ntoh(a[i])
+    end
+    return a
+end
+
+using Base.Threads
+
+function f5(a)
+    Threads.@threads  for i in eachindex(a)
+        a[i] = ntoh(a[i])
+    end
+    return a
+end
+
+a = rand(3, 10000000)
+
+b1 = @b f1(a) evals = 10
+b2 = @b f2(a) evals = 10
+b3 = @b f3(a) evals = 10
+b4 = @b f4(a) evals = 10
+b5 = @b f5(a) evals = 10
+
+
+ds = CDFDataset("/Users/zijin/.cdaweb/data/THB_L2_FGM/thb_fgl_gseQ_thb_l2s_fgm_20210120000000_20210120235959_cdaweb.cdf")
+var = ds["thb_fgl_epoch16"]
+@b Array(var)
diff --git a/test/runtests.jl b/test/runtests.jl
index 8d8f507..5d1766d 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -71,12 +71,17 @@ end
     @test var[1:3] == Float32[6.7, 6.7, 7.3]
     @test var["UNITS"] == "nT"
     @test var["FIELDNAM"] == "BR (RTN)"
+
+
+    @test ds["Epoch"][1] == DateTime(2024, 9, 1, 0, 0)
+    @test ntoh(hton(ds["Epoch"][1])) == DateTime(2024, 9, 1, 0, 0)
+
     @test @allocations(ds["BR"]) <= 50
     @info @allocated(ds.attrib)
     if VERSION >= v"1.12"
         @test @allocated(ds.attrib) <= 30000
     else
-        @test @allocated(ds.attrib) <= 65000
+        @test @allocated(ds.attrib) <= 70000
     end
 end