Tell me how does a french hour work?

Here is a list of the times to help you.. It's like military time

01h00 ~ 1:00 am
02h00 ~ 2:00 am
03h00 ~ 3:00 am
04h00 ~ 4:00 am
05h00 ~ 5:00 am
06h00 ~ 6:00 am
07h00 ~ 7:00 am
08h00 ~ 8:00 am
09h00 ~ 9:00 am
10h00 ~ 10:00 am
1100 ~ 11:00 am

12h00 ~ 12:00pm
13h00 ~ 1:00pm
14h00 ~ 2:00pm
15h00 ~ 3:00pm
16h00 ~ 4:00pm
17h00 ~ 5:00pm
18h00 ~ 6:00pm
19h00 ~ 7:00pm
20h00 ~ 8:00pm
21h00 ~ 9:00pm
22h00 ~ 10:00pm
23h00 ~ 11:00pm
24h00 ~ 12:00 am

The French don't have words for "a.m." and "p.m." You can use "du matin" for a.m., "de l'apr猫s-midi" from noon until 6p.m., and "du soir" from 6p.m. until midnight, but time is usually expressed on a 24-hour clock. Thus 3pm would be translated as quinze heures or 15h00.

Official time in France (and much of Europe) is expressed using a 24-hour clock as the other poster mentioned. Official time means theatre times, train and plane schedules, and things of that nature.

If you're in a conversation with friends, you can use either official time or the more casual "7 o'clock" (sept heure). AM or PM is often obvious from the context of the conversation. For example, if you're arranging to meet for dinner at "huit heure", you can assume that means PM.