Had to reset clocks after using batteries

[h2ofun]

I had a 5 hour outage the other day and ran off batteries. After power was restored, most of my grid based clocks had to be reset. Some had gained minutes. Anyone else see this?

 

[jjrandorin]

If the frequency is not 60hz, this can happen. there are a lot of results if you google "how does power frequency effect clock times".

Here is a link to one, but there are a lot of them:

Power grid change may disrupt clocks

A yearlong experiment with the nation's electric grid could mess up traffic lights, security systems and some computers - and make plug-in clocks and appliances like programmable coffeemakers run up to 20 minutes fast.

phys.org

So, depending on how much solar, frequency, etc, this is not unexpected.