The Day Out of Time marks the end of one solar cycle and the next.
The Day out of Time, which falls on July 25 each cycle, is the day before the new year.
The new year begins with July 26th and ends with July 24, only 364 days. The missing day is The Day Out of Time, giving the calendar 365 days.

This topic and others such as Day out Of Time is explained here, and perhaps you'll understand why it is celebrated.

Kin 13
Red Cosmic Skywalker
I Endure in order to Explore
Transcending Wakefulness
I seal the output of Space
With the Cosmic tone of Presence
I am guided by the power of navigation
Castle 1: Red Eastern Castle of Turning
Wavespell Red Dragon

Waning Crescent
Waning Crescent