Confucism:
Man with one watch know what time it is, man with two, never sure.
That's funny. I have two PCs on my desk and a phone. All three have the time. I recently visited the national observatory website and set the time of all three to within a minute of each other. The problem was two pcs read times about 20 minutes apart and the phone somewhere in the middle. It drove me crazy for months but I was too lazy to fix it.