Time

HOUR:
A hour may be represented in a numerical value of 1 to 12 or 0001 to 2400. Several digital clocks and computers running Microsoft Windows utilize civilian time of hours of 1 to 12 and represent the time of day with AM or PM. Many Unix, Linux and other clocks may use military time, which has no AM or PM and is represented with a value of 1 to 24. Below is a listing of Military time values and their conversions.

MINUTE / SECOND:
A minute is represented in numerical values of 01 to 59. There are 60 minutes in every hour and 60 seconds in every minute.

TIME ZONES:

The world is broken into 24 separate time zones that are used to help determine the time in all areas of the world. GMT (Greenwich Mean Time) or UT (Universal Time) is a method of referencing the time differences across the world. The GMT or UT is centered in the middle of the time zone as 12:00. Any time zone to the left of this is -GMT or -UT and  any time zone to the right of this is +GMT or +UT. Below is a listing of time zone abbreviations, time zone descriptions and the UT difference.

DAYLIGHT SAVING TIME AND SUMMER TIME:

Daylight Saving Time, or DST for short, is time when time in most portions of the United States and other portions of the world where time gains or loses an hour on a specific date. DST is still being used today as a means to help conserve energy.

In the United States, DST is on the first Sunday of April where clocks are set ahead one hour. On the last Sunday of October, clocks are set back one hour. In 2007 Daylight saving time will start being observed from the second Sunday in March until the first Sunday in November.

Many other countries have a "summer time", but often do not change their clock time. For example, the European Union runs from the last Sunday in March to the last Sunday in October.

Additional questions related to time

At what point does time change from AM to PM?

AM changes to PM and PM changes to AM at the stroke of 12:00.

• Additional information on how to set the computer's date and time can be found on document CH000554.
• Additional information about viewing the date in Windows can be found on document CH000555. 
• Additional information about why a computer may be losing time and/or information, or how to replace a computer's CMOS battery can be found on document CH000239.

Also see: A.M., Access time, Connect time, Deceleration time, Disk access time, Downtime, Epoch, Holdup time, Idle time,  Link time, Measurement, NTP, P.M., Real-time, Recovery time, Response time, Run time, Seek time, Settling time, Tick, Time out, Time sharing, Time-slice, Time stamp, Timer, Transfer time, Uptime