Suggest a timer chip
Rather than a stand-alone timer chip, I'd suggest using an extreme low power microcontroller such as the PIC18F24J11.  It has a hardware RTC and consumes just 830 nA in sleep mode with the RTC running.  It has a 10-bit, 10-channel ADC so you can do your voltage measurements with it also.

Available in a DIP package for prototyping for $3.18, and under $2 in a SMT package in production quantities if this is for a product.