Eternal Calculus

Eternal Calculus is a 5★ weapon in Honkai: Star Rail.

Eternal Calculus was released on January 1, 2001. They were introduced alongside Moment of Victory, Night on the Milky Way, Cruising in the Stellar Sea, But the Battle Isn't Over, Elation Brimming With Blessings, Something Irreplaceable, Texture of Memories, Solitary Healing, On the Fall of an Aeon, Sleep Like the Dead, In the Name of the World, Hey, Over Here, For Tomorrow's Journey, Before the Tutorial Mission Starts, Time Waits for No One, suggesting they were part of the same content update.