ok, bug report:
-) some stunts doesn't show up in the stunt's list. like "trust fund baby"
-) something strange happening with the journal: when i insert a in-game date different from the real world date, both change in a strange way.

How do the dates end up different?

if i insert a GM date, then, when i switch to RW date or add a new journal entry it changes in something like: 0201/01/02 or 0201/00/01

Is this only a Fate Core thing, or does it happen with other game systems?

Core and M&M3rd.
Not tested in other game systems