Support sub-second resolution in GDAL Features' datetime fields

[Tilman Koschnick]

Hi,

I have a GPX DataSource with points that have sub-second resolution:

<trkpt lat="47.454540000" lon="8.573658000">
  <ele>436.900</ele>
  <time>2025-09-25T12:24:42.990Z</time>
</trkpt>

The GDAL API returns these only with second resolution, although the underlying datetime presentation is still accessible with the as_string() method:

>>> point
<django.contrib.gis.gdal.feature.Feature object at 0x7f99254b9190>
>>> point.get('time')
datetime.datetime(2025, 9, 25, 12, 24, 42)
>>> point['time']
<django.contrib.gis.gdal.field.OFTDateTime object at 0x7f99253212b0>
>>> point['time'].as_datetime()
(c_int(2025), c_int(9), c_int(25), c_int(12), c_int(24), c_int(42), c_int(100))
>>> point['time'].as_string()
'2025/09/25 12:24:42.990+00'

In my case, I lose information, and end up being at different locations at the same time ;)

Would it be possible to support sub-second resolutions in the GDAL API? As I understand it, OGR_F_GetFieldAsDateTime() is used to return the datetime object:

​https://gdal.org/en/stable/doxygen/ogr__api_8h.html#a47ca681bb6099eb8c18004d1f7112d95

GDAL also provides OGR_F_GetFieldAsDateTimeEx() that returns seconds as float with millisecond accuracy:

​https://gdal.org/en/stable/doxygen/ogr__api_8h.html#a748995fa28574b25f6b723013a405a8f

I unfortunately don't understand the GDAL API enough to provide a patch myself.

Regards, Til