The DFRobot Gravity: I2C SD2405 RTC real-time clock module supports I2C communication and features a compensation circuit to correct crystal oscillator deviations. It keeps track of seconds, minutes, hours, day, date, month, and year, with leap-year compensation, and supports both 12-hour and 24-hour modes.

The built-in rechargeable battery allows automatic switching between the main power supply and the battery. The module generates periodic clock pulses and features three alarms, a clock output with selectable frequency, and a countdown timer with interrupt. It also includes 12 bytes of SRAM and can be used in data loggers and timing applications.

• Type: Real-time clock module
• Operating voltage: 3.3–5.5 V
• Low-power consumption: Typically 1 μA with the built-in battery at 25 °C
• Operation without external power: 5–8 years
• Timekeeping range: Through 2099
• Accuracy: ±5 ppm from -40 °C to +85 °C
• Interface: I2C up to 400 kHz at 4.5–5.5 V
• Alarms: 3, with settings for year, month, date, day of the week, hours, minutes, and seconds
• Square-wave output: Selectable frequency from 32.768 kHz to 1/16 Hz
• Time format: 12-hour or 24-hour
• Memory: 12 bytes of SRAM
• Dimensions: 35.5 × 22 mm
• Weight: 6 g
• Package contents: Gravity I2C SD2405 RTC module, 4-pin Gravity I2C sensor cable, 5-pin XH2.54 header