This isn't something that is very difficult. However, I often find I need to do the conversion from total number of seconds (example: 5412s) to the number of hours, minutes, and seconds that is (hh:mm:ss - 1:30:12 in this case). Here is a little snippet in Python that does this.

secondsToHMS

# secs is the total number of seconds
secs = 5412

# calculate things..
hours = secs / 3600
minutes = (secs - hours * 3600) / 60
seconds = secs % 60

# now print the results!
print '%02d:%02d:%02d' % (hours, minutes, seconds)