まさか、 「11AM」 の一時間後が 「12PM」 だなんて...
よく見かけるので調べてみたら...
<?php
date_default_timezone_set('UTC');
//date_default_timezone_set('Asia/Tokyo');
for ($h = 0; $h < 24; $h++) {
$time = $h * 60 * 60;
printf('%s - %s - %s %s' . "\n",
date('H:i', $time),
date('h:i a', $time),
date('h:i A', $time),
$h % 12 === 0 ? '*' : '');
}
00:00 - 12:00 am - 12:00 AM *
01:00 - 01:00 am - 01:00 AM
02:00 - 02:00 am - 02:00 AM
03:00 - 03:00 am - 03:00 AM
04:00 - 04:00 am - 04:00 AM
05:00 - 05:00 am - 05:00 AM
06:00 - 06:00 am - 06:00 AM
07:00 - 07:00 am - 07:00 AM
08:00 - 08:00 am - 08:00 AM
09:00 - 09:00 am - 09:00 AM
10:00 - 10:00 am - 10:00 AM
11:00 - 11:00 am - 11:00 AM
12:00 - 12:00 pm - 12:00 PM *
13:00 - 01:00 pm - 01:00 PM
14:00 - 02:00 pm - 02:00 PM
15:00 - 03:00 pm - 03:00 PM
16:00 - 04:00 pm - 04:00 PM
17:00 - 05:00 pm - 05:00 PM
18:00 - 06:00 pm - 06:00 PM
19:00 - 07:00 pm - 07:00 PM
20:00 - 08:00 pm - 08:00 PM
21:00 - 09:00 pm - 09:00 PM
22:00 - 10:00 pm - 10:00 PM
23:00 - 11:00 pm - 11:00 PM
まじか...
Usage Note: By convention, 12 AM denotes midnight and 12 PM denotes noon. Because of the potential for confusion, it is advisable to use 12 noon and 12 midnight.
American Heritage Dictionary Entry: PM
そうなのですか...
覚えておきます。