ISL1208 Real Time Clock
The ISL1208 is a low-cost I2C real time clock with very few external components. The calendar is accurate through 2099, with automatic leap year correction. It also features 2 bytes of battery-backed SRAM, and a configurable open-drain fOUT/IRQ pin.
A 32.768kHz crystal, and a 0.1μF bypass capacitor on VDD are the only external components required to implement the ISL1208. If battery backup is required (and it usually is), a second 0.1μF bypass capacitor should be connected to VBAT.