Just thought I would share the results of some digging I had to do when a problem arose.
I shoot Canon raw so this might not be applicable if your camera records a time zone (or offset)
1. Using exiftool, I determined that downloading CR2 files showed no field or entry for TimeZoneOffset (TZO) in exif.
2. On conversion to dng, a field, TZO is created in exif which has an entry of 0 0 for GMT and 1 1 for GMT +1 hours etc. The spaces in 0 0 etc are intentional.
3. Nothing wrong with that so far except that because Canon (many others?) has no field set by the camera for Time Zone, Adobe (in their undoubted wisdom!) take the TZO from the computer time and zone.
So the effect of this is that having converted all my raws during this autumn (and straddled the BST change at the end of October) a raw taken in Cyprus at GMT + 2 hours converts to a dng with a TZO of either 0 0 or 1 1 dependent on whether the conversion took place pre or post the last sunday in October.
'So what' I can here you say, 'TZO is only meaningful if you want to synch across more than one time zone'. 'Not so' replied I with alarming alacrity, Lightroom among other apps, changes the time of Date Time Original etc when the computer time zone or Summer time changes'.
Moral: Never trust a Dobe Wallah