How is a long timer implemented?
The bottom line is for a time delay this long you need an arrangement based around a counter driven by an oscillator. Trying to do the delay in a single analog circuit just requires unreasonably high R and C values.

In days gone by you would build a oscillator with something like a 555 and then use counter chips (cascaded if necessary) for the counting. Nowadays though the cheapest option is almost certainly a small 8 pin micro controller with internal oscillator.