The DS1302 is a Real Time Clock Module and has an SPI interface through which the time can be determined.
31×8 RAM for scratchpad data storage
Serial I / O interface for minimum pin count
Wide operating voltage: 2.0 ~ 5.5V
Single-byte and multi-byte transfers for clock or RAM data read / write
TTL compatible (Vcc = 5V)
Operating temperature: 0 to +70 degrees Celsius
32.768KHz crystal oscillator
Equipped with 260mAh CR2032 button battery, non-rechargeable
NOTE: Doesn’t include battery.