How do I set a calculation to be on one timeline or another?

By putting it on a sheet with that timeline. 

Each sheet in Openbox has a timeline associated with it. You can see this by the letter at the top right of the sheet. In the image below, the “Ops” sheet is on a Quarterly basis, and the “Construction” sheet is on a Monthly basis. 

If no letter is shown, your model only has one timeline.

If you put a calculation on a sheet that has a monthly timeline, that calculation will be done monthly. If you move the calculation to another sheet with (say) a quarterly timeline, the calculation will now be done quarterly.

The easiest way to set a sheet’s timeline is to right click on it and choose “Put on secondary axis” or “Put on primary axis”. 

For inputs, you can set the timeline individually. Just right click on each input and choose “Flip to primary axis” or “Flip to secondary axis”.