First Sunrise is thought to be one of the oldest Stenza holidays (perhaps second only to Migration), and its earliest observances are completely lost to the fog of time. However it is thought that the practices of an'o at this time (potentially including a prototypical version of They Love Each Other and They Love Us) and the use of the first true rise of Iradae and Lan'tha to mark the new year are survivals of these ancient celebrations. The earliest festivals for which records exist involved dancing, storytelling, and some of the earliest known Khe'drakha poems. By the time the Stenza began building permanent settlements many elements were firmly entrenched, including retellings of The Litany of Creation and many early versions of They Love Each Other and They Love Us, and games and a general celebratory atmosphere were becoming readily apparent. This trend would continue until the Battle with the Stone Menace, when most observances of all holidays were subdued or suspended entirely while the Stenza dealt with an existential threat. Following victory over the Stone Menace, but before the debates about what a unified Stenza entity would mean for clan customs, the new year was marked with the biggest showing of festive spirit seen in years. The debates concluded by allowing individual clans to maintain their own customs so long as they avoid civil war (which has failed on at least one occasion). As a result of the early years of the Unified Stenza Clans, many First Sunrise celebrations also include Khe'drakha about Iradae the Lawgiver and his role in bringing everyone together and keeping them that way.
Stenza astronomers keep a running calculation on when Iradae and Lan'tha will rise for the region around the Ice Flats, thereby keeping everyone up to date as to when exactly the year begins (very frequently independently of what reckoning Parevia gives for when the day actually begins). So it is popular for Stenza to spend the hours in advance of the occasion in tense anticipation, and even count down to the big movement (akin to New Year's celebrations in other parts of the universe). The Sunrise itself is met with much rejoicing. Pups and adults alike may roar or otherwise whoop, holler, and make a racket. This kicks off several days worth of an'o, Khe'drakha recital, storytelling, games, drinking, and occasional roughhousing. The Sunrise Drum sees a lot of use during the festivities, as do specific dance forms such as They Love Each Other and They Love Us. Along with Midwinter and Last Sunset, First Sunrise typically sees a reduction in Stenza troop movement.
While virtually everyone is involved in the festivities, as Iradae and Lan'tha give light and warmth to all, religious experts have the particular task of keeping an eye on revelers in case of religious experiences (which can happen to the old and the young alike) and provide needed assistance in those cases. Drummers, an'o performers, and Khe'drakha performers are also expected to be at top form, although less formal an'o and storytelling have more lax rules.
The festivities officially begin when both suns are confirmed to be rising, which in the modern day is calculated out far in advance of the actual date. This marks the official start of the new year, and the date on which it occurs (however early or late as demarcated by Parevia) is 1 First Sunrise. (Occasionally the rest of the calendar is tweaked to fit the astronomy.)