timer circuit

I was looking for a timer circuit to power my neon signboard and this is what i found (please view attachment for the circuit design). This is a 4 hour timer. What changes do i need to do to make this work for 12 hours instead of 4?View attachment 4 Hour Timer..doc

I hope you're not asking the same question again.
https://www.electro-tech-online.com/threads/help-in-simple-put-oscillator.104784/#post855936

Why not post your scematic in PNG format which any computer can read rather than Word which requires MS Office to read?