Canon EOS 90D Advanced User's Manual page 518

Setting the Date, Time, and Time Zone
The date, time, and time zone settings may be reset when the camera is
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stored without the battery, when its battery becomes exhausted, or when
it is exposed to below freezing temperatures for a prolonged period. If this
happens, set them once again.
After changing [Zone/Time diff erence], check that the correct date/time are
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set.
Auto power off time may be extended while the [ 5 : Date/Time/Zone] screen
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is displayed.
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