I need to calculate a date in SharePoint (e.g. adding seven days to a start date in order to get the due date), and if the start date is blank, then the calculated field is showing a date in the 1900s. How can I fix this issue?
You need to use the ISBLANK function for this plan to work. Here's an example:
=IF(ISBLANK([Start Date]),"00/00/00",( [Start Date]+7))
If the Start Date is blank, then the calculated field will be populated with 00/00/00. If it isn’t blank, then it will be the start date plus seven days.