How can I set up a 12 hour timer?

I want to trigger a mechanism once every real-time 12 hours. Is this possible, or well out of the realms of plausibility?

I'm using the Direwolf modpack.

Yes

The simple way is to use a timer with a ridiculously long time set. However, since you can only increment the time 10 seconds at a time, this would require 4320 clicks. A bit much.

We can do better with a simple circuit that uses maths to extend the time between pulses.

The number of seconds we want to count is 43200. This can be expressed as 2^6 x 3^3 x 5^2, or 64 x 27 x 25. These three coprime numbers can be used as the times on three timers, with the results anded together. They will then only all pulse in step once every 12 hours.

All you need to do then is sync the timers by powering them on from the same line to disable them, and then powering them all off at the same time.