Frankly, as I noted on the mailinglist - this is precisely the data, which I would store explicitly in struct dive and struct divecomputer.

Yes, we can definitely consider storing it there as well - but this will not give us much unless we surface it to the user in some form. And when it comes to surfacing it, 'Extra Info' seems to be a good place at the moment.

In extra_data, I would store things like "Central European daylight saving time".

After looking through libdivecomputer, I don't think any of the current dive computer models support this granularity - 'offset from UTC' seems to be the best they can do.