ya even they do used the timers…
you just forget this one write a new on your own… it will mostly solve your problem….
you can also use RTC they are made especially for this porpose… but i never used it….
http://www.engineersgarage.com/electronic-components/rtc-ds12c887
http://www.engineersgarage.com/microcontroller/8051projects/interface-rtc-12c887-AT89C51-circuit
http://www.engineersgarage.com/microcontroller/8051projects/alarm-clock-rtc-12c887-AT89C51-circuit