This Real Time Clock (RTC) is the most precise you can get in a small, low-power package. It is in a beefy package because the crystal is inside the chip! And right next to the integrated crystal is a temperature sensor. That sensor compensates for the frequency changes by adding or removing clock ticks so that the timekeeping stays on schedule. Besides, there is also an EEPROM AT24C32 to supply you 32K EEPROM to store your data, it is the best choice for your application that needs recoding time, With a coin cell plugged into the back, you can get years of precision timekeeping, even when main power is lost. Great for datalogging and clocks, or anything where you need to really know the time.