First of all, note that the columns are just a regular aggregation like any other (e.g. the rows or items aggregation).
There are two options I can think of:
a) Programmatically: Destroy the columns aggregation (see destroyColumns in the API doc) and then manually adding columns via addColumn based on the date range that you have.
b) Model-driven: as the columns a regular aggregation, you can bind them to a model. You would then need to populate the model based on the date range and then, the columns update accordingly.See the documentation on aggregations for details: SAPUI5 SDK - Demo Kit
Personally, I would prefer option b. You can play around with those approaches. Make sure to include a code sample (e.g. JSBin) if you get stuck anywhere along the way.
- Max