1971 Year of Decimalization (Decimal Currency was Introduced)
The solution to the ditloid "50 d in a y" is "50 days in a year." A ditloid is a type of word puzzle where numbers and letters represent a phrase or saying. In this case, it refers to the number of days typically found in a year.
Millimetres in a Yard
17 yak liquorish
Two 'O's in Google and Yahoo!
one score years
4 to 6 for dinner
1 hole in a donut
1 Hump on a Dromedary
60 Minutes in a Degree
180 degrees in a radian
70 years of marriage is a platinum anniversary
1 Birthday Every Year