Funny New error for me today.
The SharePoint list date needs to be increased by 1 year. Seems simple, right.
However last year this item was done on 29 Feb on a Leap year, and there is no 29 Feb this year, so the Workflow is failing to update the year, because the year is invalid.
Error message:
The DateTime represented by the string is not supported in calendar System.Globalization.GregorianCalendar.
The Fix
Do a simple replace of the Date String
replace({DataString},'-02-29','-02-28')
