DS1307 vs DS3231 RTC Comparison

Both are popular RTC ICs on the same I2C address (0x68). Here's when to use each.

DS1307: older design, requires external 32.768kHz crystal. Typical accuracy is ±2-3 minutes per month (±30-50ppm depending on the crystal quality). No temperature compensation. Very cheap ($0.30 bare IC). Good for projects where time drifting a few minutes per month is acceptable.

DS3231: integrated temperature-compensated oscillator — no external crystal needed. Accuracy is ±2 minutes per year (±2ppm). The integrated temperature sensor can be read over I2C. More expensive ($1-2 for bare IC, $2-4 for a module with battery backup). Also provides two alarms with interrupt output.

For any project where time accuracy matters (data logging with timestamps, scheduled events, calendar functions), use the DS3231. The DS1307 is only appropriate for non-critical 'roughly correct time' applications or extreme cost sensitivity.