Issues creating All Day Events in Outlook

Hey, everyone.

I'm using Zoho Flow to sync approved leave requests in Zoho People to a calendar in Outlook. However, the event is not being created, and gives me this error.

Outlook says "Your request can't be completed. The duration of an event marked as All day must be at least 24 hours."

Leave entries don't give times because it's all day. I had assumed that clicking "All Day Event" would make it work. Here's what's being passed to Outlook. Any suggestions? Maybe I can add the time to the date I fill in?

{
	"Time zone": "UTC",
	"Start date time": "10/01/2021",
	"Optional attendees": "",
	"Reminder - Minutes before start": "",
	"Is all day event?": true,
	"End date time": "10/01/2021",
	"Calendar": "{calendar id}",
	"Title": "Employee Name 13 - Vacation",
	"Is reminder on?": "",
	"Required attendees": "",
	"Body HTML": "<div>Origins<br></div>"
}