exiftool cheatsheet
Times
Adjust the hour and the time zone offset, including the Canon Tags.
Take an hour
exiftool -overwrite_original -TimeZoneCity=Chicago -TimeZone=-05:00 -alldates-=1 "-offsettime*=-05:00"
exiftool overwrite_original -alldates-=3 "-offsettime*=-07:00" -TimeZone=-7:00 -TimeZoneCity#=30 -verbose test.CR3
Geotag
exiftool -progress -overwrite_original -geotag foo.gpx DIR