hi! I've got a pile of links for you, so settle in...

First up, the FAQ has a couple of posts on Hours, minutes, and seconds

Origins

• Has everyone always used a 24 hour day?

• As far as I can tell, nearly all of the world divides a day into 24 hours, each of which in turn divides into 60 minutes. When and how did this come about, and were there any radically different systems of time that we've now lost? - Sumeria, also China, Japan, Scandinavia

• How did people decide on how many seconds there would be in a minute, how many minutes in an hour, and how many hours in a day? - Babylon

• How/when did we develop measurements of time? - Babylon

• When did the hour-minute-second system of measuring time (in particular, using base 60) become the world standard, and what other ways of measuring times of less than one day have been common? - Babylon

• What is the history of time(keeping)? - Mesopotamia, also Mesoamerica

• When was our concept of time developed? How did other cultures in the past measure time? When did the world agree to the 24 hour day? - also Inuit

• How did an hour become an hour? - Europe

• In a world that can't agree on anything else, how did we all come to use hours, minutes and seconds?

Other systems

• What were the common ways of time measurement in ancient Egypt and Mesopatamia? - Egypt

• Have we always used a 12 or 24 hour clock for measuring time? [x-post from /r/AskHistory] - Rome, China, Japan, Maya

• Did Far East Asia use the same standard units of time measurement (seconds, hours, days) that we use today? - China

• Did/Do native Americans have their own time system ? - Alaska