What is UTC Time?
Weather observations around the world (including radar observations)
are always taken with respect to a standard time. By convention, the
world's weather communities use a twenty four hour clock, similar to "military" time based on the 0° longitude meridian, also known as the Greenwich meridian.
Prior to 1972, this time was called Greenwich Mean Time (GMT) but is now referred to as Coordinated Universal Time or Universal Time Coordinated (UTC). It is a coordinated time scale, maintained by the Bureau International des Poids et Mesures (BIPM). It is also known a "Z time" or "Zulu Time" commonly abbreviated with a "Z".
To obtain your local time here in the United States, you need to subtract a certain number of hours from UTC depending on how many time zones you are away from Greenwich (England). The table (right) shows the standard difference from UTC time to local time.
The switch to daylight savings time does not affect UTC. It refers to time on the zero or Greenwich meridian, which is not adjusted to reflect either changes either to or from Daylight Saving Time.
However, you need to know what happens during daylight savings time in the United States. In short, the local time is advanced one hour during daylight savings time. As an example, the Western Time zone difference from UTC is a -7 hours during daylight savings time rather than -8 hours as it is during standard time.
(PST) Pacific Standard Time subtract 8 hours from UTC. (PDT) Pacific Daylight Time subtract 7 hours from UTC.
Pacific Daylight Time starts at 02:00 on the second Sunday in March. We set our clocks forward one hour.
Pacific Standard Time starts at 02:00 on the first Sunday in November. We set our clock back one hour.
| UTC | PST | PDT |
| 0000 | 4p* | 5p* |
| 0100 | 5p* | 6p* |
| 0200 | 6p* | 7p* |
| 0300 | 7p* | 8p* |
| 0400 | 8p* | 9p* |
| 0500 | 9p* | 10p* |
| 0600 | 10p* | 11p* |
| 0700 | 11p* | 12m |
| 0800 | 12m | 1a |
| 0900 | 1a | 2a |
| 1000 | 2a | 3a |
| 1100 | 3a | 4a |
| 1200 | 4a | 5a |
| 1300 | 5a | 6a |
| 1400 | 6a | 7a |
| 1500 | 7a | 8a |
| 1600 | 8a | 9a |
| 1700 | 9a | 10a |
| 1800 | 10a | 11a |
| 1900 | 11a | 12n |
| 2000 | 12n | 1p |
| 2100 | 1p | 2p |
| 2200 | 2p | 3p |
| 2300 | 3p | 4p |
*The previous day |
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