If you have a page with a Date/Time Picker open when midnight passes, the picker's "Today" button will still reference the previous day rather than updating in real time. This is an edge case specific to the date picker library Bubble uses.
What you might notice
After midnight passes with the page still open, the Date/Time Picker's "Today" button still refers to the previous day
Workaround
Refresh the page at midnight to get the Date/Time Picker to update to the correct day.