Hi Andrew,
Thanks for the question. I'll need a bit more information from you to properly debug this, if you don't mind.
1. When you say the end date is not working correctly, do you mean that nothing changes in it when you click -1? It stays the same?
2. Do the other buttons (-30, +30, +1) work as required?
3. Are you working on a custom screen, or the stock work order list screen? (You can find out by hovering over the "Work Order List" tab -- if the yellow tag says "FieldService_WorkOrderList", you're on the stock screen)
4. Which browser are you using? Have you tried any other browsers?
Let me know if you have any trouble finding this information.
Thanks,
Naeem