Date rolled back 1 day

I have a Last Read field which, obviously, I add the date I last read the book. This field can only hold a single date.

I also have a My Comments field, where I sometimes write my thoughts on the book, particularly if I really loved it, or if I really hated it. In the My Comments field, I also add the last read date to the list.

I have noticed on some books (about 15 so far) the dates are now mismatched. The Last Read field seems to have rolled back one day. So far I have only noticed it affecting books that have a 2021 date.

Does anybody know why this has happened?

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