Universal Time – UT

Universal Time or UT is the precise measure of time used as the basis for all civil time-keeping. Although their exact definitions differ, most readers can assume that Universal Time is equivalent to Greenwich Mean Time or GMT. Universal Time is actually based on the mean sidereal time as measured in Greenwich, England. It’s also approximately equal to mean solar time from Greenwich.

Like most other astronomical calculations, eclipse predictions are usually presented in terms of Universal Time. In order to convert eclipse predictions from UT to local time, you need to know what time zone you are in. For North Americans, the conversion from UT to local time is as follows:

Atlantic Standard Time (AST) = UT – 4 hours
Eastern Standard Time (EST) = UT – 5 hours
Central Standard Time (CST) = UT – 6 hours
Mountain Standard Time (MST) = UT – 7 hours
Pacific Standard Time (PST) = UT – 8 hours
If Daylight Saving Time is in effect in the time zone, you must ADD one hour to the above standard times.

For example, let’s assume that an eclipse begins in Toledo, Ohio on June 20 at 20:25 UT. Toledo is in the Eastern Standard Time zone, so:

Local Time = 20:25 – 5 hours
= 15:25 (= 3:25 pm)
But since Toledo observes Daylight Saving Time in June, we must ADD one more hour to the above time. So the eclipse will begin at 16:25 (=4:25pm) local time.

This information was taken from NASA Eclipse Website. Click here for more information.

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