What date though? Some possibilities I thought of-

March 22 (date the pilot first aired)

September 27 (date of the first slide by Quinn and the rest of the original 4 sliders)

September 24 (Quinn perfects the timer)

September 25 (Quinn's basketball is the first object returned after a slide thanks to the timer).

Any other suggestions? Of the ones listed, I think I like September 27 the best.