My first experience with time was the rabbit in Alice in Wonderland. I couldn't wait to be able to tell time and get my own watch (sadly, it wasn't a pocket watch). Since then, I've learned to see time through so many different lenses.
The 12-hour clock divides the day into two 12-hour segments (midnight to noon and noon to midnight). Thus, 2 o'clock in the afternoon is 14:00 on the 24-hour clock.
I come from a country that uses the 12-hour clock, but I much prefer transportation schedules that use the 24-hour clock. It means there's less chance of being mistakenly booked on a flight that departs before my connecting flight arrives. In fact, many countries use the 12-hour clock when conversing, but use the 24-hour clock in timetables.
Sounds simple? Not so fast.
Many African cultures use the 12-hour clock, but start the cycle at 6 a.m. (sunrise) rather than 12 a.m. (midnight). In East Africa, this is known as Swahili time (click here to see what time it is on a Swahili clock). In other words, 6 a.m. to 7 a.m. becomes the first hour of the day. You can think of this first hour as 00:00 to 1:00 on the 24-hour clock. Imagine the confusion if you schedule a meeting by asking for "2 o'clock"? Unless the exact time is clarified, your African colleague might think you meant 8 in the evening (2 o'clock = the start of the third hour of the cycle, which is at 8 in the morning or evening, according to certain African cultures). Confused yet? When scheduling appointments, it's important to specify morning, afternoon, or evening if using the 12-hour clock. Alternatively, you could use the 24-hour clock considering it starts at midnight.
In Thailand, there's a different twist on time. Thais divide the clock into four 6-hour segments: 07:00-12:59, 13:00-18:59, 19:00-00:59, and 01:00-06:59. When speaking among themselves, Thais divide the day into four 6-hour segments. Therefore, "1 in the evening" is the first hour of the 19:00-00:59 segment, or 7 p.m. on the 12-hour clock, 19:00 on the 24-hour clock. Click here for more information from Wikipedia on the six-hour clock.
And, check out AFAR's beautiful mix of clocks from around the world.