The Endless Day is a nickname for the Rosemary's second day in the Mansion. A large number of events occur on this day. The term is used by fans and by the author.
Basement society has termed() it The Day That Changes Everything.
The Endless Day began from this strip on August the first 2003 to this strip on July the 16th 2013. The Endless Day took almost ten years to make making it seem endless, hence its name.