Here's a better fix, which I'll propose as part of my next major patch. It keeps the transition times asis, without any tricks and without using 24:00, by using May 1 and Oct 1 when lastSat 24:00 does not equal lastSun 00:00. (As it happens, I got the transition times wrong in Toronto anyway: Shanks says they were at 02:00, not at 00:00. I must have copied the Montreal entries. Oops. The following part-of-a-patch fixes that too.) @@ -951,10 +961,13 @@ Rule Mont 1922 only - Apr 30 2:00 1:00 D Rule Mont 1924 only - May 17 2:00 1:00 D Rule Mont 1924 1926 - Sep lastSun 2:30 0 S Rule Mont 1925 1926 - May Sun>=1 2:00 1:00 D -Rule Mont 1927 1937 - Apr lastSat 24:00 1:00 D -Rule Mont 1927 1937 - Sep lastSat 24:00 0 S -Rule Mont 1938 1940 - Apr lastSun 0:00 1:00 D -Rule Mont 1938 1939 - Sep lastSun 0:00 0 S +Rule Mont 1927 only - May 1 0:00 1:00 D +Rule Mont 1927 1932 - Sep lastSun 0:00 0 S +Rule Mont 1928 1931 - Apr lastSun 0:00 1:00 D +Rule Mont 1932 only - May 1 0:00 1:00 D +Rule Mont 1933 1940 - Apr lastSun 0:00 1:00 D +Rule Mont 1933 only - Oct 1 0:00 0 S +Rule Mont 1934 1939 - Sep lastSun 0:00 0 S Rule Mont 1946 1973 - Apr lastSun 2:00 1:00 D Rule Mont 1945 1948 - Sep lastSun 2:00 0 S Rule Mont 1949 1950 - Oct lastSun 2:00 0 S @@ -973,12 +986,14 @@ Rule Toronto 1922 1926 - Sep Sun>=15 2:0 Rule Toronto 1924 1927 - May Sun>=1 2:00 1:00 D Rule Toronto 1927 1928 - Sep lastSun 2:00 0 S Rule Toronto 1928 only - Apr lastSun 2:00 1:00 D -Rule Toronto 1929 only - Apr lastSun 0:00 1:00 D -Rule Toronto 1929 only - Sep lastSun 0:00 0 S -Rule Toronto 1930 1937 - Apr lastSat 24:00 1:00 D -Rule Toronto 1930 1937 - Sep lastSat 24:00 0 S -Rule Toronto 1938 1940 - Apr lastSun 0:00 1:00 D -Rule Toronto 1938 1939 - Sep lastSun 0:00 0 S +Rule Toronto 1929 only - Apr lastSun 2:00 1:00 D +Rule Toronto 1929 only - Sep lastSun 2:00 0 S +Rule Toronto 1930 1931 - Apr lastSun 2:00 1:00 D +Rule Toronto 1930 1932 - Sep lastSun 2:00 0 S +Rule Toronto 1932 only - May 1 2:00 1:00 D +Rule Toronto 1933 1940 - Apr lastSun 2:00 1:00 D +Rule Toronto 1933 only - Oct 1 2:00 0 S +Rule Toronto 1934 1939 - Sep lastSun 2:00 0 S Rule Toronto 1945 1946 - Sep lastSun 2:00 0 S Rule Toronto 1946 only - Apr lastSun 2:00 1:00 D Rule Toronto 1947 1949 - Apr lastSun 0:00 1:00 D