DS-1302 from Maxim (data sheet download) is a cheap RTC chip. Below are some of the salient features. Real-Time Clock Counts Seconds,Minutes, Hours, Date of the Month, Month, Day of the Week, and Year with Leap-Year Compensation Valid Up to 2100 Simple 3-Wire Interface 2.0V to 5.5V Full Operation TTL-Compatible (VCC = 5V) 31 x… Continue reading DS-1302 RTC Clock Module for Arduino