How to add Index Column based on date condition

Hello All,   I have a below table Date Number 2/3/2023 12:00:00 AM 160 4/14/2023 12:00:00 AM 161 5/16/2023 12:00:00 AM 162 6/23/2023 12:00:00 AM   163 7/23/2023 12:00:00 ...