Using TIME to measure event duration

I understand that the TIME utility can be used to measure the duration of command execution...

Can anyone give me an example, for instance, about how to measure how long it takes to 'build world'?
There are two 'time' commands actually, both are slightly different. There's the CSH time(1) builtin and there's /usr/bin/time. I prefer the latter because it has some handy options:
/usr/bin/time -h make buildworld

The -h switch will print the time info in "human" readable format.
Thanks for explaining the '-h' switch... I ran time -h and got 'Command not found' - now I know why.