For this client, the fieldwork start and end dates for a particular month are inconsistent. For example, for Jan 2022, field work could run from the 1st to the 31st, while in 2023, it could spill over to the first week of February. He gets an SPSS file where the agency creates all the variables for the month and year. He would like to use these variables to create moving averages rather than date and time variables to set up monthly periods.