Daylight saving time 夏时制
（重定向自Day Light Saving Time）
![Most of the world's countries do not use daylight saving time, but it is common in Europe and North America.
DST used
DST formerly used
DST never used](/Images/godic/202501/08/DaylightSaving-World-Subdivisions4748.png")
![Ancient water clock that lets hour lengths vary with season.](/Images/godic/202501/08/Clepsydra-Diagram-Fancy4748.jpeg")
![G. V. Hudson invented modern DST, proposing it first in 1895.](/Images/godic/202501/08/George-Vernon-Hudson-RSNZ4748.jpeg")
![Clocks are advanced by one hour during the very early morning at the beginning of DST.When DST ends, clocks are set back (as if to repeat one hour) during the very early morning. Specific times vary by jurisdiction.](/Images/godic/202501/08/Begin_CEST_Transparent4748.png")
Daylight saving time (DST) or summer time is the practice of advancing clocks during summer months by one hour so that evening daylight lasts an hour longer, while sacrificing normal sunrise times. Typically, regions with summer time adjust clocks forward one hour close to the start of spring and adjust them backward in the autumn to standard time. People use the terms" spring forward" and " fall back " when referring to this.