I think I had the same issue and figured it out. If you want to make a new donation for a different date do this:
On the Home screen click the year's donation tab you want to work on, for example "2018 Donations." If you have more items to add for a different date click "Edit" in the items box. That brings up your "2018 Item Donations." Don't hit the "Add" button in the list of donations (or donation since I/we couldn't add another date) where "Add, Edit, and Delete" are, but click "Add Item Donation" under the donation totals and you'll then be able to start a new date.
I hope this is what you needed help with and it solves it for you.