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?


1 Answer 1



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
    Commented Jul 22, 2011 at 22:44
  • 22
    @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
    Commented Jun 3, 2013 at 16:51
  • 6
    @rajah9 this is actually why i asked this question in the first place ;)
    – Jason
    Commented Jan 7, 2014 at 18:34
  • 7
    @rajah9 That's why I'm here :). I wanted to properly name my variable.
    – Bob
    Commented Oct 29, 2019 at 14:29
  • 6
    Also here to properly name a variable. :) Commented May 16, 2020 at 0:59

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