Circadia Senius began his scientific career when humans made contact with the insect-like Circadians and established a jointly held colony world called Pax Colony. Senius was curious to understand how life could evolve so differently from his own and eagerly but shyly started studying the history of both the human race and the Circadians.
Once he was old enough, Senius left Pax Colony for Earth, where his interest in history led to a curiosity about the mechanics of time. Senius helped found Metropolis's Time Institute through his efforts to seek out and correspond with other chronal investigators. Senius identified the other principal researchers to the governing board of the Institute, but initially would not contact them in person to offer them professorships, fearing a loss of face if they declined. When the team was finally assembled, Senius was coerced into accepting the position of Chronarch despite his desire to simply stay in the background and study.
Senius met the Legion of Super-Heroes when they save the Time Institute from damage caused by the Guardians of the Universe, who interfered with the Time Institute's attempt to view the beginning of Time.
Since then, Senius has been a great ally to the Legion often assisting them with issues involving time travel.
Senius is a close friend to Brainiac 5 and Rond Vidar.