I understand you read 2000 aloud as twenty hundred hours and 0000 as zero hours.

How then do you read 0001 and 0010?

  • 1
    i think 1 second? and a 10 minute? would be better?
    – Java D
    Aug 14, 2013 at 7:18
  • 3
    @JavaD Where does seconds come into it?
    – TrevorD
    Aug 14, 2013 at 12:50
  • 1
    If I were reading it strictly in 24 hour format, I would read "0000" as "zero hundred hours" - not just "zero hours" as in the question. (But see my answer below.)
    – TrevorD
    Aug 14, 2013 at 13:33
  • What about "zero hundred one" and "zero hundred ten"?
    – GEdgar
    Aug 14, 2013 at 14:06
  • related: english.stackexchange.com/a/122325/44619
    – Mari-Lou A
    Aug 15, 2013 at 5:35

2 Answers 2

  • 0001: zero zero zero one (hours)
  • 0010: zero zero ten (hours)

Sometimes, instead of zero, oh is used, although this is a more colloquial form. From what I have read, whether or not the "hours" part is pronounced depends on the branch of military; usually it is understood to be implicit and thus left out.


  • Do you mean you say "zero zero zero one hours in the plural form" or "zero zero zero one hour in the singular form?"
    – Fujibei
    Aug 14, 2013 at 7:20
  • Added some clarification.
    – iterums
    Aug 14, 2013 at 8:39
  • Why the assumption that this question has anything to do with the military?
    – TRiG
    Sep 12, 2013 at 13:49

This is an expanded and edited version of my original answer, with additional material included primarily to address various comments below my original answer suggesting that:

  • "I take the asker's writing of both the numerical values and their pronunciations to be indications that he is indeed asking about how the times are said in a military context, rather than in generic English contexts around the world."
    [Response: OP's question does not mention "military" at all; the numeric format and terminology is not restricted to the military as explained below. OP has not commented on this point.]
  • "the 24-hour system ... is not the same as the military system"
    [Response: The formal military system is one format of the 24-hour system, and differences/similarities between it and civilian usage vary. "The 24-hour clock ... is popularly referred to as military time in [various] countries." See quotations and discussion below.]
  • "hours and minutes (and seconds) are ... always separated by something in the 24-hour system, while they are never separated in the military system"
    [Response: Both separated and unseparated formats are permitted by ISO 8601 and are in common usage, as shown below.]


The 24-hour clock is the convention of time keeping in which the day runs from midnight to midnight and is divided into 24 hours, indicated by the hours passed since midnight, from 0 to 23. This system is the most commonly used time notation in the world today, and is the international standard (ISO 8601) notation for time of day. ... It is popularly referred to as military time or astronomical time in the United States, Canada, and a handful of other countries where the 12-hour clock is still dominant.
Wikipedia 1

ISO 8601 uses the 24-hour clock system. The basic format is [hh][mm][ss] and the extended format is [hh]:[mm]:[ss].

  • [hh] refers to a zero-padded hour between 00 and 24 (where 24 is only used to notate midnight at the end of a calendar day).
  • [mm] refers to a zero-padded minute between 00 and 59.
  • [ss] refers to a zero-padded second between 00 and 60 (where 60 is only used to notate an added leap second).

So a time might appear as either "134730" in the basic format or "13:47:30" in the extended format.
It is also acceptable to omit lower order time elements for reduced accuracy: [hh]:[mm], [hh][mm] and [hh] are all used.
Wikipedia 2

Military time

Although the 24-hour system of writing time is often "popularly referred to as "military time in the United States, Canada, and a handful of other countries where the 12-hour clock is still dominant" 4, in much of the rest of the world it is now the normal format for writing times unambiguously without using "a.m." and "p.m.", especially in schedules, timetables, and many other documents. (In fact, personally, I now get confused when looking at websites that do not display the time in 24-hour format.)

The previous answer gives a link to a website for "Tell-Military-Time", and also refers to possible differences between different of the military. It would appear that that site actually describes usage within the US Military. Personally, I would be hesitant is assuming that any usage described there corresponds to common usage within other English-speaking countries worldwide. That would be especially so, because within the military, they are speaking with others trained in using the same terminology, whereas in the 'outside world' you may be speaking to someone not familiar with particular terminology.

Numeric format

As indicated in the extract quoted previously, the ISO standard permits the presence or absence of separators between the digits representing the hours, minutes and seconds. But it does specify that, when a separator is used, it should be a colon.

In the past, some European countries used the dot on the line as a separator, but most national standards on time notation have since then been changed to the international standard colon. In some contexts (e.g., U.S. military, some computer protocols), no separator is used (e.g., 2359). 5

See the following examples:

Some airlines use a colon separator [Image source]: Virgin Atlanic timetable extract

Several UK railway timetables use no separator symbol, but use a small space [Image source]: Southern Railway timetable extract

Several UK bus companies use no separator at all [Image source]: Compass Bus timetable extract

[I have found many other examples of each format, but will not illustrate or list them here.]

Speaking the time

Reverting now to OP's basic question of how to express 24-hour time in speech, military protocols may specify exact formulae, but in civilian usage:

Personally, I would not refer to:

  • 0001 as zero zero zero one hours
  • 0010 as zero zero ten hours

for fear that it may be misunderstood as "one hour" or "ten hours" after midnight. I would probably say:

one minute past midnight
ten minutes past midnight

but, depending who I was talking to, I might use any of the following:

midnight oh one
zero hours one minute
twelve oh one †
one minute past twelve †

† if it were already clear that we were referring to midnight and not noon.
Or any other similar expression that came to mind.

In summary, my answer to the questioner would be that (outside the military and other officialdom) there is no formal set way of expressing times in the 24-hour clock, and I would suggest expressing it in any suitable unambiguous manner that would be understood by the person to whom you are talking, even if that means 'translating' the time into a traditional or 12-hour format.

  • I have never seen the format used in the question used in anywhere other than military and programming. I use the 24-hour system, but that is not the same as the military system—for one thing, hours and minutes (and seconds) are in my experience always separated by something in the 24-hour system, while they are never separated in the military system. Also, times are read differently: 21:00 would never be read as ‘twenty-one hundred hours’, but simply as ‘nine o’clock’ (or similar). Aug 14, 2013 at 13:35
  • To be more clear, I take the asker's writing of both the numerical values and their pronunciations to be indications that he is indeed asking about how the times are said in a military context, rather than in generic English contexts around the world. Aug 14, 2013 at 13:38
  • @JanusBahsJacquet His question refers specifically to the "24-hour time system". He does not refer to the "military system" at all, which is mentioned only in the other answer. OP's name appears to be Japanese, but with no indication where he is from. Maybe he is in Japan and learning English and has seen that format. Who knows?! One answerer apparently made one assumption based on the format in the question. I made a different assumption based on the question's title. I disagree that 21:00 would never be read as ‘twenty-one hundred hours’. What is your basis for that statement?
    – TrevorD
    Aug 14, 2013 at 14:18
  • @JanusBahsJacquet To be more clear, you may make whatever assumption you like from the question. I may make a different assumption. That is no reason for making your disagreement so vehement. The question is ambiguous in a way that I had not realised: I would have no objection to you having pointed that out in a 'neutral' manner, but I take strong objection to the tone of your comments. And if the downvote was yours, then at least have the courage to indicate so, as is recommended in the site FAQs.
    – TrevorD
    Aug 14, 2013 at 14:26
  • Any vehemence or tone perceived in my comment lies entirely in your interpretation; the comment was meant to be entirely neutral. The basis for my statement that ‘21:00’ would never be read as ‘twenty-one hundred hours’ is, as for the orthographic separation of hours and minutes, that I have never heard it. “24-hour time system” is ambiguous to me (being any system that is based on a day having 24 unique hours, rather than 12 repeated hours, military or not), but the notation “2100” and the mentioning of hundreds is not. The downvote was not mine; it was subsequent to my comment. Aug 14, 2013 at 16:00

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.