12:30 – when it’s a.m. and p.m.

Secretary Today reader Heidi F. asked how to write the time 30 minutes after midnight and 30 minutes after midday in English. She wasn’t sure which is a.m. and which is p.m.

Here’s my answer to this interesting question:

First of all, you have to decide whether to use the 24-hour or the 12-hour clock. If you choose the 24-hour clock, 30 minutes after midnight is 00:30, without a.m. or p.m. If you choose the 12-hour clock, 30 minutes after midnight is 12:30 a.m. and 30 minutes after midday is 12:30 p.m.

Midnight Midday
00:00 12:00
12:00 a.m. 12:00 p.m.

30 minutes after midnight:

00:30 or 12:30 a.m.

30 minutes after midday:

12:30 or 12:30 p.m.

You might find this site interesting: wwp.greenwichmeantime.com/gmt-converter.htm

By the way, you can write am/pm or a.m./p.m. I prefer a.m./p.m., because I want to avoid confusion with the German word ‘am’. They are also preferred by American style manuals.