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I have laptop with dual boot(windows 8.1 pro + Ubuntu 16.04 LTS). when windows turned on after Ubuntu being in use, its time will change which become prior to the current time by 2 hours. For example: if the current time is 4:30 PM it became 2:30 PM and it is synchronized with the internet time. So why this happens? and how to fix that?

marked as duplicate by DavidPostill Mar 25 '18 at 13:39

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  • Which internet time server is it syncronised to? – Ultrasonic54321 Mar 25 '18 at 12:32
  • I have tried three different ones: time-a.nist.gov time-b.nist.gov time.windows.com – Muhammad Aldakkak Mar 25 '18 at 12:35
  • Are both systems on the same timezone? – Ultrasonic54321 Mar 25 '18 at 12:45
  • This is a long-standing problem with dual-boot systems: each realises independently that daylight-saving time has changed since the last boot and makes the adjustment. Either your internet time settings are wrong on one or other system, or synchronisation is set to be done too infrequently - weekly is fine for clock drift, but not for this situation. I don't know if it's still true, but Windows used to change the real-time clock, whereas Unix applied a software offset: you can check the time in your BIOS to see if the clock has changed. I suspect it has. – AFH Mar 25 '18 at 12:51
  • @DavidPostill - Excellent reference, thanks. Brings me up to date! – AFH Mar 25 '18 at 13:45

You can set the clock to sync time with NTP servers to avoid this problem.

  • time-a.nist.gov, time-b.nist.gov, time.windows.com, time.nist.gov, time-nw.nist.gov ==> only those servers I have, I don't have NTP server – Muhammad Aldakkak Mar 25 '18 at 12:39
  • Those are all NTP servers.... – Ramhound Mar 25 '18 at 13:08
  • The issue isn't a clock drift, it it just the different ways Windows and Linux handle the real-time clock, see link provided at top. – xenoid Mar 25 '18 at 17:11

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