A historical record is dated 17 September 1921. What was its weekday?

Correct answer: Option A — Saturday. Counting total odd days up to this date, or using a verified Gregorian calendar calculation, gives weekday index 5 where Monday is 0; therefore the day is Saturday. Option B (Sunday) is rejected because it does not equal the computed result; it represents a counting, direction, leap-year, interval, or hand-motion error. Option C (Monday) is rejected because it does not equal the computed result; it represents a counting, direction, leap-year, interval, or hand-motion error. Option D (Wednesday) is rejected because it does not equal the computed result; it represents a counting, direction, leap-year, interval, or hand-motion error.