Why can't I set a Maintenance Window that starts and stops on the same day?

I need to set an Maintenance Window from 10AM - 4PM on the same day.  I have an "Ignore" Alert Policy but I can't choose the same date in the start and stop fields.  This has been like this for years.  Why has it not been resolved?

Am I the only one who ever needs a maintenance window that doesn't span from one day to the next?