7 a.m. | 7 p.m.

I'm confused. I don't know if periods should be added after each initial in a.m. and p.m.; I'm also not sure whether AM and PM should be capitalised. I'm almost sure there should be a space between 7 and am or pm, but at the same time I think I've seen all possible combinations.

Little help? Which do you personally use, and which do you advise against using?

7 AM | 7 PM
7 A.M. | 7 P.M.
7AM | 7PM
7A.M. | 7P.M.
7 am | 7pm
7 a.m. | 7 p.m.
7am | 7pm
7a.m. | 7p.m.

I like how 7 a.m. and 7 p.m. look. Are they correct?

This is what I use personally, and by extension what I teach my students:

7 a.m.

• Use a space
• Use dots after each letter
• Use lower case

You'll get lots of different answers about this. I've noticed over the years that even among the expert members on this site, there is considerable variation.

Glizdka said:

I like how 7 a.m. and 7 p.m. look. Are they correct?

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Yes. It looks good like that, right?

No space makes it look too cluttered.
The dots break things up nicely for readability.
Capitals seems rather brash (although our American friends might disagree!).

I write 7am because it takes three fewer keystrokes and doesn't look so fussy.

Rover_KE said:

I write 7am because it takes three fewer keystrokes and doesn't look so fussy.

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Ah. All about minimising keystrokes, huh? Fair enough.

I write, and have always written, 7am and 7pm.

Not leaving a space means there is no chance of anyone thinking that "am" is an actual word (of course, the same problem wouldn't occur with "pm").

jutfrank said:

Ah. All about minimising keystrokes, huh? Fair enough.

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A lot of people are recklessly careless with their use of keystrokes. Apparently they don't realize that each person has a fixed lifetime allocation. When you use your last one, you're dea

GoesStation said:

A lot of people are recklessly careless with their use of keystrokes. Apparently they don't realize that each person has a fixed lifetime allocation. When you use your last one, you're dea

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Like with commas, right?

I imagine Rover_KE doesn't have an awful lot left.

Americans, for the most part, have abandoned periods in abbreviations. So, not "a.m." but "AM" is what I use.

7 AM

But you will see all varieties. 7 am. 7 AM. I've even been known to write something like 7:45a.

jutfrank said:

Ah. All about minimising keystrokes, huh? Fair enough.

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I do think that this is one determiner in usage- fewer people use commas in addresses now that they type their own letters and envelopes.

Tdol said:

I do think that this is one determiner in usage- fewer people use commas in addresses now that they type their own letters and envelopes.

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That is a fantastic point!

I've never thought of it like that, thank you. Do you think it also applies to many other style rules that some people consider mistakes, and even have a good justificiation for their opinion, but some just simply don't care?

For example, not using the apostrophe in possessives because "Why would I waste a keystroke on it?"

Ah, but there's no excuse. (Not in my case anyway.) My computer "suggests" a word with the apostrophe in it. For example, if I type "Im" it "suggests" "I'm" to me. ( have Android.)

Tarheel said:

Ah, but there's no excuse. (Not in my case anyway.) My computer "suggests" a word with the apostrophe in it. For example, if I type "Im" it "suggests" "I'm" to me. ( have Android.)

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How about "Today's the biggest event in my syster's whole life"?

I don't use spell check if that's what you mean. (It's more trouble than it's worth.) Also, I would say "This is the biggest day in my sister's life." (She has a brother who can't spell, but we all have our crosses to bear. ;-) )

Americans stopped using commas in addresses in the Seventies, long before most of us typed most correspondence. (I did, but I grew up in a family of touch-typists that was far from the norm.)

Commas in addresses? Where? At the end of each line? I've never seen that, I don't think.

jutfrank said:

Commas in addresses? Where? At the end of each line? I've never seen that, I don't think.

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Yes, exactly. When I learnt to touch type (rather a long time ago), addresses were laid out on the envelope and the top right-hand corner of a letter like this:

36, High Street,
Lewes,
East Sussex,
BN6 7QL

... and a generation before that:

Dr. I. Wright-Baddeley, M.D., F.R.S., J.P.,
Senior Registrar,
P.D.G. Lister Hosp.,
33, St. Olaf's Rd.,
CHORLTON-CUM-HARDY,
Lancs.

If a typist missed a single full stop or comma, her boss would often make her redo the whole thing.

jutfrank said:

Commas in addresses? Where? At the end of each line? I've never seen that, I don't think.

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It was the normal way to write or type an address in American English through the Sixties. The practice was suddenly dropped some time in the early Seventies.

emsr2d2 said:

Yes, exactly. When I learnt to touch type (rather a long time ago), addresses were laid out on the envelope and the top right-hand corner of a letter like this:

36, High Street,
Lewes,
East Sussex,
BN6 7QL

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Ugh, I don't like that (with the possible exception of the first).

What do you think the point was?