When creating an all day event near the end of a day, where the default end of the event will be on a new day, the event will be all day for both days. Changing the event to be an all day event for a single day does not work, the "To" always falls back to the second day.

e.g. an event created for the 23rd of February at 23:45 to 24th of February 00:15 results in a 2 day all day event, and with the "All day" toggle selected the to day cannot be set to the 23rd.