As extension to my other question: Time after midnight, user experience

Does Apple/Google/other calendars see post-midnight as very early this day, or very late this day?

I can't test it myself, but I'm curious (and confused)

If I set a date to be Monday the 1st of September 2014 at night 12:59 AM, will this actually be handled (military correctly) as Monday very early morning?


If I set a date to be Monday the 1st of September 2014 at 12:59 PM, will this actually be handled as tuesday very early morning?

No, this would be treated as Monday afternoon, just before 1pm.

Early morning on Tuesday would be Tuesday 12:59am in 12-hour format or 00:59 in 24-hour format. And while it's true that people might also describe that as "Monday night", in my opinion, you have to stick to describing it as Tuesday unless you write it in speech-like form and use the word "night".


  • The crossing point from Monday to Tuesday is midnight (00:00)
  • The crossing point from AM to PM is noon (12:00).
  • Midnight is the first instant of "AM" (edit: SOME places, not all), and can be written 00:00 in 24-hour format or 12am in 12-hour format.
  • Noon is the first instant of "PM" and can be written 12:00 in 24-hour format or 12pm in 12-hour format.

Google Calendar

When specifying a time for an event in Google Calendar, the time inputs are in 24-hour format so it's fairly unambiguous what time you are entering. If you enter a 12-hour format, such as "1:00", it corrects on blur to '01:00". Likewise "1pm" is corrected to "13:00".

Google Calendar

Apple Calendar

Apple Calendar behaves the same way:

Apple Calendar

  • Ok. A bit odd, but good they stick to the same day. So how do you choose (with AM/PM) the hour between midnight and 1 o clock at night? 00.30 AM? (doesn't exist) 12.30AM? (that's daytime) – mowgli Aug 10 '14 at 20:44
  • Could it be that you are using 24-hour format on OS? (I see you have "14:00"). If so, I think AM/PM is ignored, and 12.59 noon is assumed.. – mowgli Aug 10 '14 at 21:00
  • Yes, you'd choose 12:30am, and that does exist! The other 12:30, the one after noon, is 12:30pm. – Jamie Aug 10 '14 at 21:09
  • By the way "Midnight is the first instant of AM" is false.. 1 o clock AM is first instant of AM (one hour later) – mowgli Aug 10 '14 at 21:10
  • Yes my Google Calendar is indeed set to display times as "13:00" rather than "1pm", but the inputs accept both formats and handle them the same. – Jamie Aug 10 '14 at 21:11

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