CrossRoads:
On the other hand, a DS1307 & crystal are pretty inexpensive
DS1307 64 x 8 Serial Real-Time Clock DIP8 - dipmicro electronics
32.768kHz Crystal Cylinder - dipmicro electronics
Use two 4.7K pullups on the SCL, SDA linesBattery & holder
Lithium Battery CR2032 Ф20mm 225mAh 3V CR2032 - dipmicro electronics
Plastic Battery Holder 1-cell ø20mm PC 120591-1 - dipmicro electronicsSo, about $1.25 total?
It's the other $40 I spend to justify shipping that gets me....