I've just noticed that two birthdays were displayed wrong.

I have 5 lines:
08/11 Birthday (correct)
20/11 Birthday (correct)
24/11 Birthday (wrong, should be 25/11)
01/12 Birthday (wrong, should be 02/12)
04/12 Reminder to send monthly contribution to TMO (correct)

Clicking on the widget brings up the calendar that shows the correct birthday dates. What's going on?