What day is it without a perpetual calendar?

1. Calculation of the day of the week from AD to 1582 10.04: subtract the first two digits of the year from 18 and divide it by the remainder 7 to encode the first two digits of the year; The quotient of the last two digits of the year divided by 4 plus the sum of the remainder divided by 7 and the remainder divided by 7 is the last two-digit code; The monthly code is 033614625035; The day code is the remainder of days divided by 7. Divide the sum of four yards by 7, and generally speaking, the rest is the day of the week. Leap year is negative in February 1. Add 1 before February 28th, 0004. Second, (follow-up)