using calendar year and date from another table

I recommend getting inspiration from the 'events in progress' pattern: https://www.daxpatterns.com/events-in-progress/

I think you are saying that your policies don't have end dates, so you can follow the above pattern and just remove the end date portion.

To try to summarize quickly:

1) Create a Date table. See the following if not already familiar with doing this: https://www.sqlbi.com/articles/creating-a-simple-date-table-in-dax/

2) To get a count of active policies, something similar to the following should work:

# Active Polices ALL :=
VAR MinDate = MIN ( 'Date'[Date] )
VAR Result =
    CALCULATE (
        COUNTROWS ( 'Data Points' ),
        'Data Points'[Policy Issued Date] >= MinDate,
        REMOVEFILTERS ( 'Date' )
    )
RETURN
    Result