Exif
The Exchangeable image file format (Exif) is an image file format which adds metadata to existing image formats, such as JPEG.
To read the Date/Time tag do:
exif --tag=0x132 filename.jpg (reveals Date & Tag)
exif --tag=0x9003 filename.jpg (reveals Date and Time (original))
exif --tag=0x9004 filename.jpg (reveals Date and Time (digitized))
To set the Date/Time tag:
exif --tag=0x132 --set-value="1975:01:01 12:01:01" --ifd=0 filename.jpg
For tools that extract Exif meta data look here - Document_Metadata_Extraction#Images