Javascript Check if Local Date is After or Before the Start or end of the Day

I needed a helper script that helps calculate days in a availablity calendar

1. converts a UTC date string to a local time string
2. calculate total minutes of the day used (seconds and milliseconds do not matter to me in this case)
3. Check if start time is at the top of the day (midnight)
4. Check if the end time goes past the last minute of the day '23:59'

const avail = {
	start: '2023-09-01T05:00:00.000Z',
	end: '2023-10-01T04:59:00.000Z',
}

const avail2 = {
	start: '2023-10-02T03:00:00.000Z',
	end: '2023-10-31T15:00:00.000Z',
}

const startLocal = new Date(startDate.getTime())
const startLocalMin = (startLocal.getHours() * 60) + startLocal.getMinutes()
const endLocal = new Date(endDate.getTime())
const endLocalMin = (endLocal.getHours() * 60) + endLocal.getMinutes()

console.log({startLocalMin});


if(startLocalMin > 0){
	console.table({
		startDate,
		startLocal,
		startLocalMin,
		message: 'begins later than midnight on this day'
	})
} else {
	// todo set startDate one day later
	console.table({
		startDate,
		startLocal,
		startLocalMin,
		message: 'starts at the top of the day'
	})
}


if(endLocalMin > 1439){
	console.table({
		endDate,
		endLocal,
		endLocalMin,
		message: 'rolls into the next day a 24 hour day'
	})
} else {
	console.table({
		endDate,
		endLocal,
		endLocalMin,
		message: 'ends on or before 23:59 of this day'
	})
}