What are the three steps of the Doomsday method?

Century anchor → year's doomsday → count from the nearest doomsday date to your target.

1. Century anchor — a memorised weekday for the century (2000s → Tuesday, 1900s → Wednesday).
2. Year's doomsday — adjust the anchor by a small calculation on the last two digits of the year.
3. The date — find the nearest "doomsday date" in the target month and count the day difference, mod 7.

Each step is easy on its own; chained together they pin down any date. The next missions cover the dates (step 3), then the anchors (steps 1–2), then the full run.