I am familiar with the phrases 'sharp' and 'on the dot' to refer to times that are at the top of the hour. But I'm wondering if native speakers of English use these phrases to refer to other times, such as the half hour, quarter hour, or any hour whatsoever...

For instance, which of the following are acceptable according to standard native English usage?

Noon (o'clock) sharp
12:00 (o'clock) on the dot
4:30 (o'clock) sharp
4:30 (o'clock) on the dot
1:55 (o'clock) sharp
1:55 (o'clock) on the dot
10:23 (o'clock) sharp
10:23 (o'clock) on the dot

Note I checked ten online English Dictionaries and only one gives an example of other than the top of the hour or the bottom of the hour. Is there any significance to this?

Also, does using o'clock in any of the times phrases above change anything?

Can high be used for another time than 12, and does it refer to both midday and midnight?

What about trains and planes? I know the train can come at 12 o'clock high, but can it also come at 3:10 (o'clock) sharp or 3:10 (o'clock) on the dot? Or would it be more likely to arrive (or be scheduled to arrive) at exactly 3:10?

  • 1
    You're unlikely to hear or see the last one only because we typically schedule meetings and plan trips around the quarter hour marks. But I just Googled leaves at * sharp and found plenty of examples that aren't at the top of the hour: Bus will wait from 7:30 am and leaves at 7:45 am sharp. The activity bus for intramurals leaves at 5.45 sharp. The last bus leaves at 6:15 AM sharp. Ride leaves at NOON SHARP! You can change the query and find more, like: The train departs at 4:15 sharp, and We landed at 3:10 on the dot local time! to name a few. They all sound fine to me.
    – J.R.
    Mar 26, 2015 at 9:18
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    BTW, this question reminds me of a story that happened when I was a kid. I got stung by a bee once, right around the bridge of my nose, and a friend joked for two days: "J.R. got stung by a bee at 4:26 – right on the nose." He was pretty proud of his pun, and we were all amused by it, too.
    – J.R.
    Mar 26, 2015 at 9:23

3 Answers 3


Firstly: "o'clock" should not be used except after a number of hours, alone. "12 o'clock", yes; "12:01 o'clock", no; "noon o'clock", no. If you need to be clear that (for example) "ten fourteen" is a time, and not some other number, you could use "a.m."/"p.m." or say "fourteen [minutes] past ten".

Secondly: "on the dot", "sharp", and others are used to emphasise that a time is precise when people might think it's not. If I say "12 o'clock", you might well assume that I'm rounding to the nearest hour (or half-hour, or 15 minutes, or whatever). I could say "12 o'clock sharp" to be clear that I mean exactly 12 o'clock.

If I say "10:23", however, the fact that I bothered to specify a number of minutes, and not a nice round multiple of typical values, would suggest that I mean exactly 10:23. Saying "sharp"/"on the dot" would be redundant in this case, but not wrong.

That said, there are situations when even an atypical number of minutes might be taken as vague, and so "sharp"/"on the dot" would not be redundant:

  • When accuracy to within seconds is meant, and you want to be clear that you mean "10:23 and zero seconds". (Example: A school has morning break start at 10:23. The students want to be let out 30 seconds or a minute early, but the teacher is adamant that they will be let out at "10:23 on the dot".)

  • When atypical numbers of minutes are still only estimates. (Example: Bus timetables will give times like "10:23", but it's expected that it will likely be later. You might then tell a friend that the bus arrived at "10:23 on the dot", because you want to emphasise how unusual it was that it was there right on time!)

Lastly: "high" is (in my experience) only used with "noon"; not just the time "noon", but with the exact word "noon". The title of the movie you linked to, "Twelve O'Clock High", is not about time, it's about direction. In a military (or colloquial) context, directions relative to you can be specified by points on the clock: "12 o'clock" is straight ahead, "6 o'clock" is behind you, "5 o'clock" is behind you but a little bit to the right. And then aviators, having to deal with three dimensions, can also specify "high" or "low" (or, if I remember rightly, "level"). So the title "Twelve O'Clock High" is pilot-speak for "straight ahead and at a higher altitude".

  • Very thorough answer! I learn a lot from it! Wish I could upvote it twice.
    – RayLuo
    Aug 10, 2017 at 6:31

I think:

'sharp' and 'on the dot'

only refer to an exact time. What the time is does not matter.

I would not use o'clock other than after a whole hour, unless you want to be redundant.

top and bottom of the hour are a different issue. These refers to the position of the minute hand on an analog clock.

I have only heard 'high' in respect to high noon. Not midnight.

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    I've never heard "o'clock" for anything but a whole hour (AmE), even for emphasis.
    – cpast
    Mar 26, 2015 at 3:23
  • @cpast OK, I was probably stretching a bit...
    – user3169
    Mar 26, 2015 at 3:27
  • I don;t think you'd use sharp or on the dot as often for 10:23 as you would for 10 o'clock, because 10:23 already implies a much higher precision (down to the minute) than "10 o'clock", which in many cases could mean "somewhere around 10". So if we mean exactly 10:00, not 10:01 or 09:59, we have to indicate that we mean 10, on the dot. For 10:23 it's clear we don't mean 10:22.
    – oerkelens
    Jul 9, 2015 at 9:28

I would say that “on the dot” is about the hearer being punctual. Similarly, one might say, “The ferry arrives at 10:23am, on the dot.”, to mean that it is reliable and punctual.

(As others have said, “12 o’clock sharp” would mean precisely 12:00.)

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