On January 1, 1870, John A. Macdonald was Prime Minister.
1880 – John A. Macdonald
1890 – John A. Macdonald
1900 – Wilfrid Laurier
1910 – Wilfrid Laurier
1920 – Robert Borden
1930 – W.L. Mackenzie King
1940 – W.L. Mackenzie King
1950 – W.L. Mackenzie King
1960 – John Diefenbaker
1970 – Pierre Trudeau
1980 – Joe Clark
1990 – Brian Mulroney
2000 – Jean Chrétien
2010 – Stephen Harper
2020 – Stephen Harper?
Eric Koch’s book, The Weimar Triangle, is available at Indigo-Chapters and in your local bookstore. 
what does it all mean really?
It MAY mean that Canadians like their prime Ministers to have long tenures. (The Joe Clark interlude conceals Trudeau’s.)
Happy New Year!
What is the explanation for the almost universal infatuation with years that end in zero (and, a close second, five)?
Pythagoras may have learned in the Underworld that tens and fives are easy to multiply.
Happy New Year!
Did the Greeks have a zero?
The old Attic numeral system is decimal, uses tens and hundreds, etc., but has no zero.
The Babylonians had a numbering system with a base of 12 (IIRC which is not guaranteed). I am not sure why that translated into circles with 360 degrees, but it did, somehow.
I wonder if we would do likewise (i.e. prefer dozens to tens) if we all had an extra finger on each hand, à la Anne Boleyn.