How to define rolling 12 months period?

Question

I have a data-set that looks like this

KEY_cEFF_DT2269_1_15/1/20252269_1_14/2/20252269_1_19/2/20242269_1_18/31/20242269_1_13/25/20242269_1_13/23/20242269_1_13/21/2024  5523_1_15/28/20255523_1_14/29/20255523_1_19/29/20245523_1_19/27/20245523_1_14/21/20245523_1_14/19/20245523_1_14/17/2024

How would I go about adding a "ROLLING_TWELVE_MONTH_PERIOD"(365 das) where the calc starts at the MIN EFF_DT for each KEY_c so the results look like this

KEY_cEFF_DTTwelve Month Period2269_1_15/1/202522269_1_14/2/202522269_1_19/2/202412269_1_18/31/202412269_1_13/25/202412269_1_13/23/202412269_1_13/21/20241   5523_1_15/28/202525523_1_14/29/202525523_1_19/29/202415523_1_19/27/202415523_1_14/21/202415523_1_14/19/202415523_1_14/17/20241

SPetrie · Accepted Answer

Here is one method. You need to get your dates into an actual date format in order to get a time difference. Then You grab the minimum date per key and use it to compare.

I used the ceiling of the difference in days divided by 365 to get the 1 or 2 values and a formula to clean up the 0 values for same dates.