# How ignition historian daylight saving

**URL:** <https://forum.inductiveautomation.com/t/how-ignition-historian-daylight-saving/41298>\
**Category:** Ignition\
**Created:** [December 8, 2020, 3:54pm UTC](https://forum.inductiveautomation.com/t/how-ignition-historian-daylight-saving/41298 "2020-12-08T15:54:51Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![nader.chinichian](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/nader.chinichian/32/9261_2.png) [@nader.chinichian](https://forum.inductiveautomation.com/u/nader.chinichian)\
**Post date:** [December 8, 2020, 3:54pm UTC](https://forum.inductiveautomation.com/t/how-ignition-historian-daylight-saving/41298/1 "2020-12-08T15:54:51Z")

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Hello,  
I’d like to know what is proper way to handle daylight saving when we have GPS time server with ignition.  
The GPS server automaticaly the time for daylight saving in gateway OS. This cause some overlap to older data in ignition historian. Specially when we have 1 month partitioning.  
Can someone explain me how ignition handle this situation and differ between overlap data?

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**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\
**Post date:** [December 8, 2020, 4:07pm UTC](https://forum.inductiveautomation.com/t/how-ignition-historian-daylight-saving/41298/2 "2020-12-08T16:07:28Z")

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Last I looked close, the timestamps in the historian tables are 64-bit integer UTC milliseconds, so there should be no overlap.