I've noticed a full stop (period) after "UTC" on the Enthusiast badge page. In my understanding, the presence or absence of the period after the abbreviation doesn't seem to affect the meaning.

Are there any style guides that recommend using a period in abbreviations? I'm curious to know the conventions in this context.

Screenshot for reference:

Abbreviation with full stop

In a plain text:

Visit the site each day for 30 consecutive days. (Days are counted in UTC.).

  • 15
    It's marking the end of a sentence - the one in the brackets - and would be present whether or not there was an abbreviation before it. However, the full stop after the brackets probably shouldn't be there. Nov 30, 2023 at 17:39
  • 5
    What @SteveMelnikoff said. Except the full stop after the brackets definitely shouldn't be there. The entirety of the bracketed "parenthetical" element must be capable of being removed without affecting the validity of what's left (that's why its terminating full stop goes inside the brackets). If Days within the brackets hadn't been capitalised, the period before the opening bracket would have to be removed - but then the period inside the brackets would be unwanted! Nov 30, 2023 at 18:35
  • 5
    This is something that's changed in my lifetime. When I was at school it would have been U.T.C. or N.A.T.O. Today its the norm to treat strings of capital letters abbreviating something as a word, with no periods. The fact that it's a string of capitals is quite enough to indicate what it is.
    – nigel222
    Dec 1, 2023 at 10:20
  • 1
    @nigel222 Agreed: capitals provide sufficient indication of an abbreviation, making a full stop redundant — and so we tend not to use the full stop there, to avoid ambiguity with its other functions.  That's why lower-case abbreviations such as ‘p.m.’ and ‘etc.’ still need a full stop — and why those are awkward and becoming rarer.  (‘etc.’ doesn't work in upper case, which is why I prefer using the more concise ‘&c’ instead.  But I gather it's not universally understood…)
    – gidds
    Dec 1, 2023 at 11:55
  • 1
    @nigel222 - me too, though I don't miss them, they feel better without. There's also a tendency to call any abbreviation an acronym, where that use to be reserved for those you pronounce rather than spell; scuba, laser, NATO, NASA etc. Such as HHGTTG are still abbreviations to me, not acronyms. Dec 1, 2023 at 14:50

2 Answers 2


The answer to your actual question, as mentioned elsewhere, is that UTC [nor any capitalised abbreviation in similar form] does not take a full-stop [period].

However… the sentence as written in the badge description is actually wrong, because it appears to give UTC a stop… then gives the sentence another stop, outside the brackets.

Because the entire sentence is enclosed within the brackets, the one inside is correct and ends the sentence. The one outside the brackets is spurious - and incorrect.

  • If you remove the one after UTC, it becomes accurate. So, that's enough.
    – Lambie
    Nov 30, 2023 at 19:12
  • 13
    @Lambie - no it doesn't. The one inside the bracket is correct. The entire sentence is inside, so the stop should be too. The one outside is wrong. Nov 30, 2023 at 19:21
  • 2
    Oh yeah, the other way round. Right.
    – Lambie
    Nov 30, 2023 at 19:22

The full stop (period) does not apply to UTC. It applies to the sentence UTC is contained in.

UTC does not contain a full stop.

Definition of UTC

The sentence inside the brackets takes the period, not UTC.

  • 2
    That's kind of half-right, but there's a bigger issue. Nov 30, 2023 at 18:58

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