aggregation of annual rainfall daily data to 2-day and 3-day without crossing next year

Hi All,

I want to create a column from my daily rainfall data to sum the value of the current day and the next one to create a 2-day aggregate over the whole year and for 3-day...etc. The problem I am having is the last daily value of the current year is summed up with the value of next year. Is there a way to restrict the summation to the year. I have attached a sample and highlighted the issue in yellow. Thanks

Regards