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Transitioning Into Daylight Saving Time

The World Clock features a list of cities where you can view information about that city including if it observes Daylight Saving Time.

How does the transition start?

For example: DST starts at 2:00 am local time and DST will move the clocks forward one hour - the seconds before and after the "Spring forward" are listed in the following table:

DST start transition
Local timeDST or standard?Comments
1:59:58standard 
1:59:59standard 
3:00:00DSTDST starts, time advanced by one hour
3:00:01DST 
3:00:02DST 

Note that the local time between 2:00:00 — 2:59:59 does not exist during the transition from standard time to DST. This hour is skipped, therefore this day only consists of 23 hours.

Anyone who worked during the night from midnight to 8:00 a.m. has worked only seven hours because of the skipped hour.

How does the transition to DST end?

For Example: DST ends at 2:00 a.m. local time and the switch back to standard time will move the clocks back one hour:

DST end transition
Local timeDST or standard?Comments
0:59:59DST 
1:00:00DST 
1:00:01DST 
time from 1:00:02 to 1:59:57 daylight saving time not shown
1:59.58DST 
1:59.59DST 
1:00:00standardTime is turned back to standard time
1:00:01standard 
time from 1:00:02 to 1:59:57 standard time not shown
1:59.58standard 
1:59:59standard 
2:00:00standard 
2:00:01standard 

Note that the local time from 1:00:00 to 1:59:59 is repeated this day. It first occurs during DST time, then clocks are turned back one hour to standard time and the time is repeated during standard time.

To avoid confusion, when referring to time within this hour, it is important to mention whether it was before or after the change back to standard time. The day consists of 25 hours when DST ends.

Anyone who worked during the night from midnight to 8:00 a.m. has worked for nine hours because of the repeated hour.

Topics: Daylight Saving Time, Timekeeping

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