Time off is where requests are submitted, approved or denied, and where you see what is already booked.
The flow
Someone submits a request. It sits as pending until it is approved or denied. Approved time off shows on the forward view of the next couple of months; a cancelled request drops out.
Requests can be filtered by status, so the pending ones are one click away rather than mixed in with everything already settled.
Why it belongs next to the schedule
A holiday approved without looking at the work booked for that week is how a service business ends up with three jobs and nobody to do them.
The forward view exists for exactly that check. Two people off in the same week is fine in February and can be a serious problem in July, and the only way to know is to look before approving rather than after.
The habit worth keeping
Approve or deny promptly, even when the answer is obvious. A request sitting untouched is read as a yes by the person who made it and as an open question by everyone else, and the gap between those two readings is where the awkward conversation comes from.