[Katsunami]

Maybe then both should be updated to fix this problem.

Sigil should then be updated to correctly handle time-zone aware dates, but I think Calibre may still need to be updated.

First, if I want to put in a publication date, and I put in 1-1-2005, 0:00, I just think it's illogical to save it somewhere in 2004, and then compensate with my time zone when displaying the date. It makes the date change when I change my timezone.

If a book is officially published at 1-1-2005, 0:00 (date/time at the book's publishing location), then it should be possible to just put that date/time into the metadata without regard to timezones. If Calibre can't do that now (if it can, I'm not aware of it), it would be best to make this an option.

Second, I assume Sigil does not include opf:event="publication" in <dc:date> just for fun. At least, FlightCrew validation does not see this as a problem. It's used to recognize the publication date from the creation and modification date of the ebook. I think Calibre should include an option to preserve opf:event="publication" (or creation, or modification) if it's there.