Editing 12-hour clock (section)

===Typography===
The terms "a.m." and "p.m." are abbreviations of the Latin {{Lang|la|ante meridiem}} (before midday) and {{Lang|la|post meridiem}} (after midday). Depending on the [[style guide]] referenced, the abbreviations "a.m." and "p.m." are variously written in [[small capital]]s ("{{smallcaps|am}}" and "{{smallcaps|pm}}"),<ref>{{cite web |last1=Trask |first1=Larry |title=Small Capitals |url=https://www.sussex.ac.uk/informatics/punctuation/misc/small |website=University of Sussex Informatics |publisher=The University of Sussex |access-date=30 October 2024}}</ref><ref name="Chicago MOS">{{cite web |title=9.39: Numerals versus words for time of day |url=https://www.chicagomanualofstyle.org/book/ed18/part2/ch09/psec039.html |website=The Chicago Manual of Style Online |publisher=The University of Chicago |access-date=30 October 2024}}</ref> [[Letter case|uppercase]] letters without a [[full stop|period]] ("AM" and "PM"), uppercase letters with periods, or lowercase letters ("am" and "pm"<ref name=ESG /> or "a.m." and "p.m."<ref name="Chicago MOS"/>). With the advent of computer generated and printed schedules, especially airlines, advertising, and television promotions, the "M" character is often omitted as providing no additional information as in "9:30A" or "10:00P".<ref>{{cite web |last=Watson |first=James Robert |title=A more efficient way to denote am or pm |url=https://www.jamesrobertwatson.com/ampm.html |website=Jim Watson professor of design |access-date=August 30, 2022}}</ref>

Some style guides suggest the use of a space between the number and the a.m. or p.m. abbreviation.{{citation needed|date=March 2011}} Style guides recommend not using a.m. and p.m. without a time preceding it.<ref>Hacker, Diana, A Writer's Reference, six edition, Bedford, St Martin's, Boston, 2007, section M4-c, p.308.</ref>

The hour/minute separator [[Date and time representation by country|varies between countries]]: some use a colon, others use a period (full stop),<ref name=ESG>{{cite book |title=Economist Style Guide |page=185 |edition=12th |isbn=9781781258316 |publisher=[[The Economist]] |date=2018}}</ref> and still others use the letter h.{{citation needed|date=October 2021}}<!-- Dubious. I have seen the h notation many times but only ever with 24-hour clock. --> (In some usages, particularly "[[military time]]", of the [[24-hour clock]], there is no separator between hours and minutes.<ref>{{cite book |author=<!--Staff writer(s); no by-line.--> |date=May 27, 2015 |title=The Tongue and Quill |publisher=US Air Force |url=https://static.e-publishing.af.mil/production/1/saf_cn/publication/afh33-337/afh33-337.pdf |page=356 |access-date=26 October 2021 |archive-date=26 November 2020 |archive-url=https://web.archive.org/web/20201126183321/https://static.e-publishing.af.mil/production/1/saf_cn/publication/afh33-337/afh33-337.pdf |url-status=dead }} Air Force Handbook 33-337.</ref> This style is not generally seen when the 12-hour clock is used.)