Thank you for your patience! You are correct. This is a bug…
So I’ll quote @Gintare from @tracker-backend:
is it possible that the date for some events in the list is provided, but doesn’t comply with the format? With csv, empty cells are probably not considered null, and then date validation fails. I would say it’s a bug
Would you like to create a Jira bug issue for this (or I can create it on your behalf if you want) jira.dhis2.org?
As for the program rule, I’m not entirely sure but I’d have used this rule (change 3 to any number):
d2:addDays(V{due_date},‘3’)
[I’m not sure PR work during the import-.- so I’m asking a question on the CoP as well (Program Rules work during/after import?)]