# Midnight? **URL:** \ **Category:** Factual Questions\ **Created:** [September 17, 2015, 4:04am UTC](https://boards.straightdope.com/t/midnight/731533 "2015-09-17T04:04:25Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![Ranger\_Jeff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ranger_jeff/32/2065_2.png) [@Ranger\_Jeff](https://boards.straightdope.com/u/Ranger_Jeff)\ **Post date:** [September 17, 2015, 4:04am UTC](https://boards.straightdope.com/t/midnight/731533/1 "2015-09-17T04:04:25Z")
Does midnight of a particular day, how about September 16th, occur one second after 23:59:59 September 15th or one second before 24:00:01 September 17th? Or does no date apply to the moment of midnight? ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [September 17, 2015, 4:15am UTC](https://boards.straightdope.com/t/midnight/731533/2 "2015-09-17T04:15:51Z")
The [National Institute of Standards and Technology](http://www.nist.gov/pml/div688/times.cfm) says that technically speaking no date applies to midnight. On a 24-hour clock, they suggest that 2400 could be used to represent midnight of the preceding date, while 0000 (which is the same time) could be used to represent midnight with respect to the following day. ---
**Author:** ![SeaDragonTattoo](https://avatars.discourse-cdn.com/v4/letter/s/df705f/32.png) [@SeaDragonTattoo](https://boards.straightdope.com/u/SeaDragonTattoo)\ **Post date:** [September 17, 2015, 4:18am UTC](https://boards.straightdope.com/t/midnight/731533/3 "2015-09-17T04:18:38Z")
The hospital where I work, where we’re creating records 24/7/365, 12:00am is the beginning of the calendar day. ---
**Author:** ![burpo\_the\_wonder\_mutt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/burpo_the_wonder_mutt/32/365_2.png) [@burpo\_the\_wonder\_mutt](https://boards.straightdope.com/u/burpo_the_wonder_mutt)\ **Post date:** [September 17, 2015, 4:31am UTC](https://boards.straightdope.com/t/midnight/731533/4 "2015-09-17T04:31:32Z")
[The Master speaks:](http://www.straightdope.com/columns/read/120/the-millennium-approacheth-will-it-start-jan-1-2000-or-jan-1-2001) ---
**Author:** ![Ranger\_Jeff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ranger_jeff/32/2065_2.png) [@Ranger\_Jeff](https://boards.straightdope.com/u/Ranger_Jeff)\ **Post date:** [September 17, 2015, 2:26pm UTC](https://boards.straightdope.com/t/midnight/731533/5 "2015-09-17T14:26:49Z")
I reckon I’ll go with the NIST. Thanks to all who responded. ---
**Author:** ![Zeldar](https://avatars.discourse-cdn.com/v4/letter/z/b77776/32.png) [@Zeldar](https://boards.straightdope.com/u/Zeldar)\ **Post date:** [September 17, 2015, 3:01pm UTC](https://boards.straightdope.com/t/midnight/731533/6 "2015-09-17T15:01:04Z")
As clear as this would appear: > [@](#): > > Is midnight the end of a day or the beginning of a day? > When someone refers to “midnight tonight” or “midnight last night” the reference of time is obvious. However, if a date/time is referred to as “at midnight on Friday, October 20th” the intention could be either midnight the beginning of the day or midnight at the end of the day. > > To avoid ambiguity, specification of an event as occurring on a particular day at 11:59 p.m. or 12:01 a.m. is a good idea, especially legal documents such as contracts and insurance policies. Another option would be to use 24-hour clock, using the designation of 0000 to refer to midnight at the beginning of a given day (or date) and 2400 to designate the end of a given day (or date). …it doesn’t really address instances such as “deadline for entries is Midnight of (such and such a date).” So it would seem necessary to add the :59 or :01 to the seconds part of the time. I can’t recall seeing that level of specificity in contests and such. Confusing! 😕 ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [September 17, 2015, 3:47pm UTC](https://boards.straightdope.com/t/midnight/731533/7 "2015-09-17T15:47:12Z")
What date midnight is associated with is undefined. However, when you look at a clock and it shows 12:00, it is unambiguously AM and the next date. ---
**Author:** ![Sage\_Rat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sage_rat/32/399_2.png) [@Sage\_Rat](https://boards.straightdope.com/u/Sage_Rat)\ **Post date:** [September 17, 2015, 8:36pm UTC](https://boards.straightdope.com/t/midnight/731533/8 "2015-09-17T20:36:43Z")
Probably all software considers 00:00 to be the start of the day and allows for no such thing as 24:00. Adding one second to 23:59:59 creates 00:00 in all of the OSs and VMs that I know. So, regardless of whether the time masters are leaving it ambiguous, almost everything that you use to tell time has decided that Midnight is the start of the next day. ---
**Author:** ![Saint\_Cad](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/saint_cad/32/18907_2.png) [@Saint\_Cad](https://boards.straightdope.com/u/Saint_Cad)\ **Post date:** [September 17, 2015, 9:10pm UTC](https://boards.straightdope.com/t/midnight/731533/9 "2015-09-17T21:10:14Z")
> [@Zeldar](#): > > As clear as this would appear: > …it doesn’t really address instances such as “deadline for entries is Midnight of (such and such a date).” So it would seem necessary to add the :59 or :01 to the seconds part of the time. I can’t recall seeing that level of specificity in contests and such. > > Confusing! 😕 Sure it does. If you turned it in at 2400 you met the deadline. If you waited until 0000 you’re too late. ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [September 18, 2015, 5:04am UTC](https://boards.straightdope.com/t/midnight/731533/10 "2015-09-18T05:04:12Z")
My auto insurance policy specifically says: “From 02-18-2015 12:01 Standard Time at the address of the Named Insured . . . To 02-28-2016 12:01 Standard Time at the address of the Named Insured.” So they resolve time down to the minute, but not down to the second.