By calculation (generator: ["day_week@trueknowledge.com"]) I know that:
Thursday
is the day of the week of
May 21st 1970
Friday
is the day of the week of
May 21st 1971
Sunday
is the day of the week of
May 21st 1972
Monday
is the day of the week of
May 21st 1973
Tuesday
is the day of the week of
May 21st 1974
Wednesday
is the day of the week of
May 21st 1975
Friday
is the day of the week of
May 21st 1976
Saturday
is the day of the week of
May 21st 1977
Sunday
is the day of the week of
May 21st 1978
By calculation (generator: ["timepoint_when_day_happened_on@trueknowledge.com"]) I know that:
May 21st 1971
is a timepoint when the day happened on
Friday, the 21st of May and 1970s
May 21st 1976
is a timepoint when the day happened on
Friday, the 21st of May and 1970s