Ok I’m moving this back to “under review” as it’s gathering a lot of interest, but this would require first https://updown.uservoice.com/forums/177972/suggestions/16982392 and https://updown.uservoice.com/forums/177972/suggestions/15589635 to be implemented to provide a decent UI for this.
An error occurred while saving the commentO. Akdemir commented
that's a great idea! We really need this feature since we have scheduled maintenance times and now they're counted as "un-available" times