hi Reigning_data 

First, you should know that:

1. Calculation column/table not support dynamic changed based on filter or slicer.
2. Measure can be affected by filter/slicer, so you can use it to get dynamic summary result.

https://www.sqlbi.com/articles/calculated-columns-and-measures-in-dax/

Then for your case, you could use 

What if parameter

for example:

Step1:

There should be a date table in the report, if not, you could try this formula to create one.

Date = CALENDAR(TODAY()-365,TODAY()+365)

Step2:

Create a what if parameter

Step3:

If you just use (today+ days) as a variable, you could try this simple formula to create a measure

Measure 1 = DATEDIFF(TODAY(),TODAY()+[Parameter Value],WEEK)

Then just use slicer to select dynamic dates.

If you want use (today+months) as  a variable, you need to use this formula to create a measure

Measure 2 = var _table= ADDCOLUMNS('Date',"_movedate",DATEADD('Date'[Date],[Parameter Value],DAY)) return
DATEDIFF(TODAY(),MAXX(FILTER(_table,[Date]=TODAY()),[_movedate]),WEEK)

here is sample pbix file, please try it.

Regards,

Lin