I have a DS1307 clock chip (I2C), a crystal and battery - on a little PC board. Interfaced to a Mega32.
Is it just my bad luck that it has lost 90 seconds or so of time since I set the clock to match NIST (atomic clock)? Each day it is a few more seconds farther behind, according to my radio clock and according to NTP setting my PCs clock.
Bad luck that I have a rotten crystal?
The little board came from SparkFun electronics.
I've got the AVR reading the date/time once a second. Is it possible that this causes the DS1307 to lose time accuracy? I assumed not.