SharePoint date & time field

Hi, Everyone ,

My company has work shift from 26/01/2018 to 25/02/2018. And there are many events which is counted by this work shift. But When i use pivot table to calculate the event which is sorted by that work shift but the data is sorted from 01/01/2018 to 31/01/2018 Would you mind to help me to change the normal shift to my company work shift.