DS1302 Real Time Clock
The DS1302 is a Real Time Clock (RTC) or TimeKeeping Chip with a build-in Trickle-Charger.
Important note : Cheap modules with the DS1302 and DS1307 have often problems with the crystal and the voltage. They often don't work very well. You are strongly advised to use a DS3231, which is very reliable and accurate and needs only a battery to run (the crystal is inside the DS3231).
This is a cheap module with the DS1302: