start from 0 as mentioned in docstring

Author: eroell

src/ehrdata/io/pandas.py

@@ -270,7 +270,7 @@ def from_pandas(
         if fill_time_gaps:
             time_key = long_format_keys["time_column"]
             current_times = xr_dataarray[time_key].values
-            full_range = np.arange(int(current_times.min()), int(current_times.max()) + 1)
+            full_range = np.arange(0, int(current_times.max()) + 1)
             # Select only the value variable before reindexing to avoid dtype conflicts
             # (e.g. datetime64 columns can't be filled with np.nan)
             xr_dataarray = xr_dataarray[[long_format_keys["value_column"]]].reindex(