Function: TIME_NIST Purpose: Returns NIST corrected system time (systime(1)) Correction is determined from NIST. (Requires internet connection). Typical computer clocks are highly variable often differing by a few seconds (or more) from UTC. This routine will return a time that is typically accurate to a few 10s of milliseconds. Time offsets are determined no more than once per hour (unless FORCETIME keyword is used) Written by Davin Larson (Feb 2012)