Reproduction steps:

• Click "Create Event" in Calendar.
• Fill in name, description, policies, etc.
• Set an invalid time for one of the dates, like the meaningless string "Tea Time".
• Click "Create" to save the event.

Expected result:

• Form reloads with an error message about the specific mistake.
• All values are preserved verbatim.

Actual result:

• Form reloads with an error message about the specific mistake.
• Most form values are destroyed.