Today I received an email from a customer, where a user was not able to move a calendar appointment by opening the appointment and entering a different date/time. He was able to move the appointment by "Drag and Drop".
The user was using IBM Notes 9.0.1 FP6 on Windows 10.
You can easily get rid of this error by simply deactivating the option "Strict Date/Time input" like mentioned in the following TN:
After removing this setting the user was able to change the date and time inside the calendar entry.