Reset Power using 555 timer
The evil 666 555 timer is inappropriate for durations as long as 30 minutes.

What you want to do can be trivially done with a tiny microcontroller, like the PIC 10F200.  It has a built in oscillator that is more accurate than what a 555 can do with common parts, is smaller, takes less power, and requires no external parts other than the bypass cap.

The firmware counts ticks to get arbitrarily long time delays.  Since this is done digitally, all derived times are as good as the internal oscillator, which is a few percent.

If low power is important, then you have the PIC sleep most of the time, counting wakeups by the watchdog timer to keep time.  The watchdog isn't very accurate, but it won't drift quickly.  I've used it in low power projects where every 1000 wakeups I kept the processor on to calibrate the watchdog against the internal oscillator.  It still sleeps 99.9% of the time, and the long term accuracy is only slightly worse than the internal oscillator.  Note that a 555 with ordinary parts can't achieve that accuracy anyway, and would draw way more power.

If power isn't the issue, keep the processor running and counting instruction cycles.  At a nominal 1 M instruction cycles per second, 30 minutes only requires a 31 bit counter, so you'd use 4 bytes (32 bits).