Day
import type { Day } from "https://esm.sh/v135/date-fns@3.6.0/index.d.mts";The day of the week type alias. Unlike the date (the number of days since the beginning of the month), which begins with 1 and is dynamic (can go up to 28, 30, or 31), the day starts with 0 and static (always ends at 6). Look at it as an index in an array where Sunday is the first element and Saturday is the last.
type Day =
| 0
| 1
| 2
| 3
| 4
| 5
| 6;