Module No. 3554
Signal Reception Precautions
When the watch is unable to adjust its time in accordance with a GPS signal for some reason, average timekeeping accuracy is within ±15 seconds per month.
Note that an internal decoding process the watch performs after it receives a GPS signal may cause the time setting to be slightly off (by less than one second).
GPS signal reception is not possible under the conditions described below.
While 
or lower is displayed for the battery level
While the watch is connected with a phone and data communication is in progress
While the watch’s Airplane Mode is enabled
While sleep measurement is in progress
If the receive operation is successful, the time and day settings will be adjusted automatically in accordance with the Home City (time zone) and summer time settings. Summer time will not be applied correctly in the cases described below.
When the summer time start date and time, end date and time, or other rules are changed by authorities
When location information is received, but it is not location information for your actual location (For example, when you are near a borderline of a city and the acquired location information is for a neighboring city, etc.)