When we moved back from Gloucester I noticed that one of my clocks was off by 8 hours. Now we have had some NStar power outages but I doubted if they were that much time over the summer. I reset it and several days later it was 10 minutes off. I thought that these simple synchronous motor clocks couldn't do this.
Anyway it had given good service; I'll bet it is at least 40 years old.