Day type overrides replace an entire day's schedule for the designated area.
This is particularly useful in the case of holidays or special events that fall on a day in which production would normally run.
If July 4 falls on a Monday, which is configured as a Weekday in the base configuration, you use a day type override to define July 4 as a Holiday.
Another example is a case where, due to increased production demands, the plant decides to run extra hours to meet these demands. If an alternate schedule and day type have been configured to meet these additional production hours, you can use the alternate day type to override the standard day type.