gh#1463 fix wrong day display in widget

[lmamane]

The bug ultimately came from the fact that:

• convertAllDayLocalToUtc and convertAllDayUtcToLocal are not guaranteed to preserve any part of the value of their recycle argument
• older implementation of convertAlldayUtcToLocal just happened to accidentally preserve recycle's timezone
• newer implementation does not; note that convertAlldayLocalToUtc already didn't preserve recycle's timezone previously
• the code in buildFromCursor assumed that recycle was preserved, in particular by passing it to populateDayInfo while the latter critically depends on recycle having the correct timezone

[Gitsaibot]

Can you please rebase.

[jspricke]

Thanks! This looks ok to me, but I did not test it.