A real-time clock (RTC) is a critical component for applications that rely on analysis of data acquired in real time. RTC accuracy of better than 5ppm is essential for credible data. While several environmental factors can affect RTC accuracy, temperature fluctuation is the most common cause of RTC inaccuracy. This application note shows how to use a MAXQ3100 microcontroller to calculate a trim factor that can be used to compensate for RTC inaccuracy caused by temperature changes.