"Let's meet Saturday night at 2 o' clock" is "incorrect" and could never happen (calendar wise)

Midnight is the start of a new day. So anything after that is the next day (again, calendar wise)

But most people knows what is means and sees 2 o' clock after midnight as the same day

For most people it does not mean Sunday morning at 2 o' clock. Especially party-people, night owls etc. ;) At least in daily speech. "See you tonight at 2 o' clock!" etc.

This makes it difficult to have a user calendar with date/time on a website

Should I put a notice: "Remember, a calendar day starts/ends at 00:00 / 12 AM"? That could confuse people

Or do people already know this when dealing with a calendar?

How do you get about it?

  • Maybe I should also look into how Apple/Google/others handle their calendar day switching..
    – mowgli
    Aug 10, 2014 at 14:33
  • Is this required as text or would a visual solution work? Aug 11, 2014 at 8:30
  • It's for text only
    – mowgli
    Aug 11, 2014 at 9:28
  • Old TV Guide magazines used to list times with two dates during such hours. For example, Late Friday / Early Saturday 2 am, Late Saturday / Early Sunday 2 am. Aug 12, 2014 at 8:17

3 Answers 3


That actually depends on the context. Imagine you're booking a flight and it says Saturday, 2am on the tickets. There's hardly any doubt that it's the night Fri-Sat and not the next night. It's a whole different thing if you're e.g. providing the running order of a music festival. Saturday, 2am there, is almost always technically Sunday, 2am, but this isn't a problem for users either as the days of a festival are logically splitted into e.g. Friday, Saturday and Sunday.

So what I'm trying to say is that you should try to get as much context as possible for users before you start adding warnings. A "Remember, the day starts/ends at 00:00 / 12 AM" warning for someone booking a flight could actually be more confusing than helpful. For someone taking track of his night out it could prove helpful though. I.e. If you provide a UI to enter events for Saturday, and the user adds an event for 2am after having added events for the same day for later times, then a warning could be helpful, if it's the first event of the day then it might be intentional.

The most important thing is to be consistent with displaying the data. Taking my examples, it would be very confusing if a concert that gets added to Sunday, 2am eventually shows up on the Saturday line-up.

  • Yes. And the closer we get to 12AM (like 10 minutes past midnight) the easier it is to misunderstand.. The date day change should happen at sunrise, not night time. Much more natural
    – mowgli
    Aug 10, 2014 at 12:45
  • It would be more natural for night owls, but not more natural for early birds. "I woke up late Saturday evening, went outside, watched the sunrise. Early Sunday morning, I ate breakfast and took a shower." ~ not natural
    – emory
    Aug 10, 2014 at 13:22
  • Well that would depend on the time for switching date. I think 3-4 o' clock would cover most (the vast majority are neither extreme night owls or extreme earlybirds). Daylight saving change is also an unnecessary mess, but let's not get into that ;)
    – mowgli
    Aug 10, 2014 at 13:44
  • There are places on this planet where the sun doesn't rise or set at all in some months of a year. These days are gonna be looooooooong. "I took a two month break from Sunday afternoon to Sunday evening"
    – msp
    Aug 11, 2014 at 14:12

The user might intuitively know what they mean when they are talking about 2am Saturday, but when it comes to interpretation by someone else, there is an element of confusion. A subtle reminder or a hint like "2am 'Saturday' is technically Sunday, but you already know." would be a great help for all parties involved.

  • 1
    Yes. Or just a "Very early morning!" if the time is between 00:00 and 6:00 (12AM to 06AM). Want to avoid forcing abstract thinking on the user ;)
    – mowgli
    Aug 10, 2014 at 10:46

Most People will know this when dealing with calendar. Notice is not necessary i believe. I would suggest to use Tomorrow at 02:00 am / Tomorrow early morning.

00:00 - 09:00  - EARLY MORNING
09:00 - 12:00 - MORNING
12:00 - 16:00 - AFTERNOON
16:00 - 20:00 - EVENING
20:00 - 23:59 - NIGHT

and so on. This will give a clear idea for the user.

  • Yes, I'm leaning towards the believe that users know that a calendar day starts/ends at midnight.. But when setting a date/time on the website, there is only date and time, not "morning/tomorrow" etc. Well, maybe it helps to limit the clock to 23:59 11:59PM
    – mowgli
    Aug 10, 2014 at 9:41
  • Hm, I'm not sure about this answer. If you show the time range it doesn't make sense to remove the minute, 20:00 - 00:00 is perfectly clear (same for 8PM - 12AM). I think most users will understand, and for added clarity you could show a little informative blurb next to /below the selector after changing selection saying 'tomorrow morning 2AM' for example? Aug 10, 2014 at 10:05
  • The thing is.. if I do something like that (show a hint), it has to be done EVERYWHERE, to avoid any extra ambiguity/confusion to all users, not just to the person creating the date
    – mowgli
    Aug 10, 2014 at 11:16

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