To avoid mistakes the chief engineer at one pit I worked at insisted all written reports were timed using the 24 hour clock,I became that use to it I still use it even after twenty years.
Pedantically, the terms AM and PM actually mean Ante (not anti) Meridiem and Post Meridiem... or as one poster has stated, before and after mid-day (noon). One source states it's a Latin phrase, of course, and "It's a dissimulation of "medius + dies" where" "Medius" is an adjective put in the locative case meaning ".
Noon or mid-day is further defined as the highest point attained by the sun in his diurnal course... (see what you've started 2sp?)
I work on fluff time, not ummmm time. I think that's the problem, it's not universally agreed which is which, but as more and more deliveries etc are done through computers, and computers don't know about noon and midnight, people have to use the figures.
I once took my daughter to the airport for her 8pm flight. Arrived to a empty airport. Her flight was 08:00. I asked her to check her ticket several times.... Shocking!!!
Being in aviation, I'd agree wholeheartedly with RATTER15... problem is the use of the 24 hour clock is, I think, a lot more accepted in Britain and Europe than it is here in the U.S. Normally only used by the military and airlines here and not understood by the general populace...