Timing in seconds

In vbscript there's a variable that holds the number of seconds since midnight or some such, is there any similar thing in Lua?

or how would I go about timing how long it takes before one function is called to when another is called?

See os.clock :

http://www.gammon.com.au/scripts/doc.php?general=lua_os


Or, for more resolution, use GetInfo (232). That gives a more precise measurement than single seconds.