Create a column with a specific date

Looks like you need a parameter for your reference date.

No need to add a column with the reference date: you can use the parameter value to calculate the aging.

But you can still add a column with the reference date, though.

Both are included in this query:

let
    Source = #table(type table[Date = date],List.Zip({List.Dates(#date(2017,1,1),20,#duration(15,0,0,0))})),
    AddedAging = Table.AddColumn(Source, "Aging", each RefDate - [Date], type duration),
    AddedRefDate = Table.AddColumn(AddedAging, "RefDate", each RefDate, type date)
in
    AddedRefDate