Date math/calculations

I am finding more and more cases where I wish I could have a calculated-date in a variable. In a few cases a kludge of adjusting to match another calculated-date variable has been "ok" but not ideal.

Would be great to be able to do date math (e.g. 10 days before, 10 days after) as a field.

I understand it would be work, but perhaps a short-term answer would be for you to define a handful of system fields that are calculated dates? 

Chuck