The DS1307 is an integrated circuit with real-time clocks. It features a simple construction and a relatively high accuracy. You can find it on all Chinese e-shops in the form of a module or a separate integrated circuit.
The integrated DS1307 has low power consumption and has 56 SRAM bytes backed by battery. Circuit clocks provide time information (seconds, minutes, hours, days, months, and years). The circuit correctly calculates the perpetual years. The circuit acts as a SLAVE device on the I2C bus. The address is 0x68.
As a module, you can find it in several variations that differ only in detail.
About DS1307 I wrote the following articles: