Do a leap-year date: what day was 29 February 2020?

Saturday.

1. Anchor (2000s) = Tuesday (2).
2. Year 20: q = 1, r = 8, s = 2 → 2 + 1 + 8 + 2 = 13, mod 7 = 6 = Saturday (year's doomsday).
3. The date: 2020 is a leap year, so February's doomsday is 2/29 — which is the doomsday. 29 February 2020 → Saturday.

Check: 29 February 2020 was a Saturday. ✓ The leap-day anchor (2/29) lands right on the doomsday, so the answer is immediate.