Converting a whole list between 24-hour and 12-hour time
Rosters, booking exports and log files come in 24-hour time, while notices and text messages are usually written with AM and PM. One or two are easy to do in your head, but past ten lines it is easy to swap 12 and 00, or write 1 PM as 11:00 instead of 13:00. Paste the list here and every line is converted at once, with the input and the result side by side.
Where noon and midnight part ways
Each time is turned into seconds past midnight and the hour is taken modulo 12. Because the 12-hour clock writes a zero hour as 12, 00:00 becomes 12:00 AM and 12:00 becomes 12:00 PM. Those two cases are counted separately and reported. Going the other way, an AM or PM marker is required: a line with neither marker, or with both, is reported by its line number.
Only the notation rules of the two clock systems are used, so as of October 2026 no external table or official recommended value is involved. Full date-and-time stamps, time-zone (UTC offset) conversion and conversion between hour, minute and second units are not supported, and up to 200 lines are accepted at once.
Frequently asked questions
In the 12-hour clock 12:00 PM is noon and 12:00 AM is midnight. So 24-hour 12:00 becomes 12:00 PM and 00:00 becomes 12:00 AM, and both cases are counted separately in the results.
Anything from 24:00 upward is rejected and the line number is reported. A day ends at 23:59:59, and midnight is written as 00:00 of the next day.
No. 9:05 AM, AM 9:05 and 9:05PM all read the same. A line is rejected only when it carries both markers or neither of them.