Greenwich mean time (GMT) or universal time (UT) is the mean solar time on the Greenwich meridian reckoned in days of 24 mean solar hours written as 00h
at midnight and 12h
at noon. To convert the above times to those of the other standard time meridians, add 1 hour for each 15o
of east longitude of the desired meridian and subtract 1 hour for each 15o
of west longitude. This table was compiled from data supplied by the Nautical Almanac Office, United States Naval Observatory.