Windows 10 automatic daylight savings adjustment not working?
Solution 1:
In general, "Adjust for daylight saving time automatically" should always be On. Turning it off is for a few legacy edge cases and a couple of places in the world that don't currently have an appropriate entry in the list of time zones.
Most likely, the system clock isn't set to the correct time. Perhaps there's a problem getting the correct time from the Internet, which is enabled or disabled from the first "Set time automatically" option.
I recommend:
Check that your Internet Time Server settings are correct. Try a different time server if necessary.
Turn on all options, being sure to turn on "Adjust for daylight saving time automatically" before turning on "Set time zone automatically".
Solution 2:
This has just happened to me this week on a Windows 10 machine, as we entered Daylight Saving Time in some regions here in Brazil, even with the "Adjust for daylight saving time automatically" enabled. Windows did recognize DST, but the clock kept on going to the wrong time zone: UTC instead of UTC-2 (DST from Brasília's UTC-3).
It has been solved by changing the NTP server to pool.ntp.org, as @MattJohnson and @stevemidgley indicated above. At first, it seemed "time.windows.com" server might not be up-to-date in its time zones settings, but the time configuration remained OK after returning the server to "time.windows.com".
What I've also noticed is that time zone settings frequently stalls on Windows 10, requiring using Task Manager to kill its processes.