Multiple users report issues with the metadata extracted from the exif.
Reports:
- https://commons.wikimedia.org/w/index.php?title=Commons:Forum&oldid=158774021#Falsche_Metadaten_trotz_korrekter_EXIF-Daten
- https://commons.wikimedia.org/w/index.php?title=Commons:Village_pump&oldid=158748778#Error_in_metadata_viewer.3F
Example file:
https://commons.wikimedia.org/wiki/File:D%C3%BClmen,_Buldern,_Skulptur_am_Gro%C3%9Fen_Spieker_--_2015_--_5497.jpg
The API returns <metadata name="DateTime" value="0 (Windows)"/>, though it should be something like April 17, 2015