For everyone GMT-7 and further West, Sync (Export) to Pure Calendar no longer worked since Day-Light Savings (due date shifts by 1-day)
It started on or about March 11. The ToDo's displayed by Pure Widget from Ultimate Todo List show-up one day early, but ONLY if the phone time zone is GMT-7, GMT-8, etc. (after daylight savings is applied if required) The Toodledo and Ultimate ToDo List show the correct date anyway. It's got to be a bug in the way the two apps exchange data. The author of Pure Calendar is aware of that, but the problem might come from Ultimate Todo List.
Have you moved from one time zone to another since you installed Ultimate To-Do List? If so, then an uninstall and reinstall of UTL will likely clear up the problem.
Didn't move really but I followed your recommendation, uninstall, reinstall, and it did solve the problem. Thanks.