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Possible mistake on question

One of the questions asks me to translate


basically meaning

"i go to sleep at midnight"

or more literally

"i go to sleep at zero a.m"

yet the only correct answer seems to be:

"i go to sleep at 12 a.m"

At first I found it confusing but after some thought I think this might actually be a mistake. As by the correct answer given by the app, "12 am" is actually midday and not midnight. Midnight would either be 12pm or 00:00am.


EDIT: After trying further exercises, it seems like 午前れい時 is always incorrectly translated to 12am (midday)

EDIT 2: According to what I've researched, midnight cannot be denominated by either 12pm or 12am as both are incorrect. Once again, just like the japanese say, "It is Zero o'clock (in the morning)". That's my suggestion for fixing the questions. Remove the twelve and the am/pm and simply add zero o'clock. That way there will be no ambiguity and you won't trick literally half of the users.

June 26, 2017



Japan uses a 24 hour clock. In the context of a 12 hour clock and a 24 hour clock, 12am and 0 are equivalent. :)

Edit: I was thinking of pm rather than am when I wrote this. (12pm and 0am are equivalent.) So, I'm not sure what's up with those sentences either. Perhaps it is an error, or it is more advanced than my understanding.


Where on Earth should I start?... I'm not sure everyone here even knows what "a.m.", "p.m.", or "o'clock" actually mean.

  • a.m. = "ante meridiem"
  • p.m. = "post meridiem"

  • 午 = meridiem (Latin for "noon/midday")

  • 前 = ante- ("before/pre-/prior" in time)
  • 後 = post- ("after" in time)

If you knew what the phrase "o'clock" means, you'd know "zero o'clock" is ridiculous and meaningless.

  • 時 = time / time period ("hour"; German: "uhr"). 時 doesn't mean specifically "o'clock" ("of the clock"). You only say the word "o'clock" when the time is 'on the hour' (unlike 時 or "uhr").

Using 24-hour clock (h:m:s.ms) :

  • 11:59:59.999 = a.m. (before noon)
  • 12:00:00.000 = meridies (noon)
  • 12:00:01.000 = p.m. (after noon)
  • 12:00:00.999 = p.m. (because noon was 999 ms ago)
  • 12:00:00.001 = p.m. (because noon was 1 ms ago)

↑ Given that 12:00:00.001 ~ 12:00:00.999 is "p.m.", wouldn't it be crazy to argue that 12:00:00 (noon) is "a.m." (before noon)? Surely you wouldn't say 12:00 is a.m. but 12:01 is p.m.?

Noon—in terms of the time on the clock—is instantaneous. At 12:00:00.000, you're no longer in the noon-not-yet-having-happened period (a.m.); you're now in the noon-happened period.

  • 23:59:59.999 = p.m.
  • 00:00:00.000 = midnight
  • 00:00:00.001 = a.m.

↑ Same here. Surely you wouldn't say 00:00 is p.m. but 00:01 is a.m.?

Also, as 00:00:00.000 is the start of the new calendar day and as noon has not occurred yet on this brand new day, isn't it most logical that this should be "a.m." ?

And as 12:00:00.000 (noon) is "12 pm" in 12-hour clock format, then midnight cannot also be called "12 pm"...

So, 00:00:00.000 (midnight)—"twelve o'clock" (the number "XII" or "12" on the clock face "of the clock")—is therefore "12 am" when in 12-hour clock format.

tldr: Midnight is neither "zero of the clock" nor "12 pm".


Also 12 am is considered midnight or 00:00am if you are using military time.


From the site of the National Physics Laboratory in the UK: "There are no standards established for the meaning of 12 a.m. and 12 p.m."

I wish they'd replace "12 a.m." with "midnight" in the exercises - that way you'd have an unambiguous expression that people actually use.


12am is midnight. I get your "logic" that 12am should be noon as 12am should come after 11am and 12pm should come after 11pm... BUT, 12:59 during the day is post-meridiem so 12:59 during the day would be 12:59pm. You can't have 12:00am followed directly by 12:01pm. The use of am or pm at exactly 12:00 is confusing and probably should avoided... BUT that is the correct convention. You can look it up.


For clarification purposes, yes, 零時 would be 12:00am, as Japan is on the 24 hour clock. There are times where I have also seen 午前12時に寝ます Which would mean the same thing, because the "gozen" indicates it was the morning 12:00am, and not the "gogo" 午後 12pm. I hope that makes sense.


For the sentence discussion of「午前れい時」, check out this page:


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