Some time ago we chronicled the restoration of the clock. The full story can be found here:
Since then we have taken the time to properly calibrate the movement to ensure that it is keeping good time. The procedure to do this is very simple as the speed of the clock is regulated by a single screw on the backside of the unit that applies more or less pressure to the internal balance wheel to control its speed and therefore the accuracy of the clock.
Horologists have the benefit of calibrating equipment that allows for the fast setting of the clock accuracy. Such equipment compares the 'beating' of the clock's heart to a known standard rate allowing for the instantaneous adjustment to what is correct. We did not have such luxuries so we relied on just the natural passage of time recorded and compared to our known standard which was satellite time as shown on my iPhone. The clock was referenced every few days over a period of several weeks until we got it as accurate as we could with timekeeping teetering between fractionally fast and slow.