After charging a new unit's battery, I set the internal clock.
The seconds did not change after setting the time, only the date, hours, and minutes. This makes it possible for the time to be off by as much as one minute immediately after setting the clock to an accurate time source.
In a later version of the firmware, it would be useful to have the seconds reset to zero at the moment when the correct minute has been typed and the Enter key has been pressed to input the new minute.