Firstly, your valves would have to be compatible with the AC solenoids... Are they? Are there two spots for a 24v transformer?

Yes, i do have these valves for AC solenoids..

And what do you mean by two spots for the transformer?

Is there a circuit board on the DC timer? And what is the model of the DC timer? I honestly don't think this will work.

Yes, but not without buying more parts and doing some circuit building ... you would have to feed the "ON" signal from the 12V timer into some sort of bridging circuit that can switch the 24V currents that open and close the solenoids.

You will get ONE chance to make this work, because running 24V through any of the components on the 12V side (if you mis-wire or miscalculate a component or have a stray current path you didn't spot) will usually result in a lot of smoke and melted circuits.

As someone who actually studied and repaired electronic control systems ... my advice would be to buy the right sort of timer for your solenoids and read the installation manual.

Ok, thank you both, i will check this out