The Ascension, on the 1st of Sypheros (October), commemorates Tira’s sacrifice. This harvest time holiday emphasizes community service. Dusk services typically feature dramatic re-enactments of the defeat of Bel Shalor¬—the assassination of Samyr Kes by servants of the Shadow in the Flame, the defeat of Durastoran the Wyrmbreaker, and finally Tira’s plunge into the fiery abyss, Kloijner hilt-deep in Bel Shalor.
Source: Cultures of Thrane
The 1st of Sypheros, 299 YK, was the date that Tira Miron and her party confronted Bel Shalor, resulting in Tira Miron sacrificing herself to re-bind the overlord. The faithful gather on this date to remember her story, of the suffering inflicted upon Thrane, and the sacrifices made by all templars since.
Many of the faithful will find a way to spend the day contributing to their communities, helping the less fortunate as a way of giving thanks to those whose sacrifices allow people to live their lives (relatively) unbothered by supernatural evils.
Source: Sarhain's Guide to the Silver Flame
On this day, worshipers remember the sacrifice of Tira Miron, who joined with the Silver Flame to become its Voice.
Source: Eberron Campaign Guide
On this day, worshipers remember the sacrifice of Tira Miron, who became the Voice of the Flame. They gather to reaffirm their faith and to thank Tira, attending great blessing ceremonies in the cathedrals. On this day, the faithful seek ways to contribute to the community.
Source: Faiths of Eberron