What is Greenwich Mean (Z) Time?

Greenwich Mean Time or Z (Zulu) Time refers to a universal 24-hour clock which runs from 0000z to 2359z. You can convert Standard/ Daylight Savings Time to Greenwich Mean Time (GMT) by first converting your local time to 24-hour time by adding 12 hours, ie. 3:00pm=1500. Then add the appropriate number of hours as shown below:

STANDARD TIME
(OCT-APR) 		DAYLIGHT SAVINGS
(APR-OCT)
Eastern Time add 5 hours add 4 hours
Central Time add 6 hours add 5 hours
Mountain Time add 7 hours add 6 hours
Pacific Time add 8 hours add 7 hours

For example, if local Eastern Standard Time is 6:00pm, convert this to 1800 on the 24-hour clock, then add 4 hours = 2200GMT or 2200Z Time. If local Mountain Daylight Savings Time is 1:00pm, convert this to 1300 on a 24-hour clock, then add 7 hours = 2000GMT or 2000Z.


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