I know that AM/PM is for ante/post meridiem, but what is it actually called? Meridian indicator? 12 hour indicator? Something way more clever?



Oddly enough, this question seems to already have been answered (and then later removed) at StackOverflow. (this is the last existing Wayback Machine backup link to it.)

  • The Unicode standard for date/time formatting calls it "period".

  • Wikipedia says: The 12-hour clock is a time conversion convention in which the 24 hours of the day are divided into two periods

  • Ruby documentation (and probably a lot of strftime references) seems to refer them as "Meridiem Indicator".

From a user interface perspective, a "Period" label is too ambiguous, and "Meridiem Indicator" too pedantic, still leaving "AM/PM" as the best choice.


As for the actual meanings of AM/PM, they come from the Latin "ante meridiem" ("before noon") and "post meridiem" ("after noon").

  • 4
    ha! wtf... why would that be asked on SO? anyways, thanks!
    – Jason
    Jul 22 '11 at 22:44
  • 17
    @Jason, because software developers think about naming variables properly. It is built into the Object-Oriented mindset. Jader, a commenter, said it well: "It's funny that the question intrinsically is not programming related, but all programmers can understand why you posted it here."
    – rajah9
    Jun 3 '13 at 16:51
  • 5
    @rajah9 this is actually why i asked this question in the first place ;)
    – Jason
    Jan 7 '14 at 18:34
  • 3
    @Json and that was the reason I found your post XD
    – BananaAcid
    Dec 28 '18 at 2:31
  • 4
    @rajah9 That's why I'm here :). I wanted to properly name my variable.
    – Bob
    Oct 29 '19 at 14:29

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