Suunto X9_en. Instruction Manual page 20

Sync
When the Sync setting is on, Suunto X9 sychronizes the current time from the satellite
signal every time the GPS is activated. You will also have to set the correct UTC Offset
for your time zone.
If Sync is off, the manually set time is not automatically updated.
the time zone. For time zones other than Greenwich time (GMT) + full or half-hours,
you have to set the time manually and keep Sync off.
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To set the time synchronization:
1.In the Set menu, scroll to Time/Date and press ENTER.
2.Scroll to Sync and press ENTER. The On/Off field is
activated.
3.Change the On/Off status with UP/DOWN and long press
ENTER. The time synchronization is now set. You return to
the Time mode's main display.
UTC offset
You can set the UTC offset at 0,5 hour intervals depending on
To set the UTC offset:
1.In the Set menu, scroll to Time/Date and press ENTER.
2.Select UTC with UP/DOWN and press ENTER. The offset
field is activated and it shows either plus or minus hours from
the GMT.
3.Adjust the offset with UP/DOWN and press ENTER. The
UTC offset is now set.
4.Press STOP/BACK to return to the Set menu.