Welcome to OpenSprinkler!
The issue you are having with the last program you described is likely related to the interval time. This is a required field and setting it to 0 prevents the program from running. For the latest OSPi, if you set the program to run a single time you shouldn’t have the issue or you can use a recurring program with a higher interval value.
In regard to the end time error the first time around, what exactly was the error?