I'm not sure if this has been discussed before, but it looks like I found a bug that potentially affects if an Event will be properly listed in the "Events List Widget" and the "List" view. This bug also seems to have the potential to affect any implementation of an Recurring Events feature in future versions.
When an all-day event is entered for the first time with *no revisions*, the event's "_EventEndDate" meta is not properly recorded. The event's date is recorded correctly, but the time is not.
"YYYY-MM-DD 23:59:00" (the event ends on the last minute of the day)
it is recorded as:
"YYYY-MM-DD 00:00:00" (the event ends on the first minute of the day)
Any revisions to the post will correct this error, but if the post is not modified, the error will remain.
Because the event is recorded as ending on the first minute of the day, any event posted once with no revisions will not appear on the widget or list view on the day of the event because after the first minute of the day, the event will be detected as being over. Also, if the upcoming recurring events feature simply duplicates a post multiple times, this bug could affect the copies too.
Temporary Workaround: The simple workaround is when entering a new all-day event, click "Publish" then after the post is entered, click "Update" so it gets a second revision.