For example:
$ bundle exec dst_differences.rb Europe/London America/New_York
+------+---------------------+------------------------+--------------------+---------------------+------------------------+--------------------+
| year | Europe/London start | America/New_York start | difference in days | Europe/London start | America/New_York start | difference in days |
| 1918 | 24 March | 31 March | 7 | 30 September | 27 October | 27 |
| 1919 | 30 March | 30 March | 0 | 29 September | 26 October | 27 |
| 1920 | 28 March | 28 March | 0 | 25 October | 31 October | 6 |
| 1921 | 03 April | 24 April | 21 | 03 October | 25 September | -7 |
| 1922 | 26 March | 30 April | 35 | 08 October | 24 September | -13 |
| 1923 | 22 April | 29 April | 7 | 16 September | 30 September | 14 |
| 1924 | 13 April | 27 April | 14 | 21 September | 28 September | 7 |
| 1925 | 19 April | 26 April | 7 | 04 October | 27 September | -6 |
| 1926 | 18 April | 25 April | 7 | 03 October | 26 September | -6 |
| 1927 | 10 April | 24 April | 14 | 02 October | 25 September | -6 |
| 1928 | 22 April | 29 April | 7 | 07 October | 30 September | -6 |
| 1929 | 21 April | 28 April | 7 | 06 October | 29 September | -6 |
| 1930 | 13 April | 27 April | 14 | 05 October | 28 September | -6 |
| 1931 | 19 April | 26 April | 7 | 04 October | 27 September | -6 |
| 1932 | 17 April | 24 April | 7 | 02 October | 25 September | -6 |
| 1933 | 09 April | 30 April | 21 | 08 October | 24 September | -13 |
| 1934 | 22 April | 29 April | 7 | 07 October | 30 September | -6 |
| 1935 | 14 April | 28 April | 14 | 06 October | 29 September | -6 |
| 1936 | 19 April | 26 April | 7 | 04 October | 27 September | -6 |
| 1937 | 18 April | 25 April | 7 | 03 October | 26 September | -6 |
| 1938 | 10 April | 24 April | 14 | 02 October | 25 September | -6 |
| 1939 | 16 April | 30 April | 14 | 19 November | 24 September | -55 |
| 1946 | 14 April | 28 April | 14 | 06 October | 29 September | -6 |
| 1947 | 16 March | 27 April | 42 | 02 November | 28 September | -34 |
| 1948 | 14 March | 25 April | 42 | 31 October | 26 September | -34 |
| 1949 | 03 April | 24 April | 21 | 30 October | 25 September | -34 |
| 1950 | 16 April | 30 April | 14 | 22 October | 24 September | -27 |
| 1951 | 15 April | 29 April | 14 | 21 October | 30 September | -20 |
| 1952 | 20 April | 27 April | 7 | 26 October | 28 September | -27 |
| 1953 | 19 April | 26 April | 7 | 04 October | 27 September | -6 |
| 1954 | 11 April | 25 April | 14 | 03 October | 26 September | -6 |
| 1955 | 17 April | 24 April | 7 | 02 October | 30 October | 28 |
| 1956 | 22 April | 29 April | 7 | 07 October | 28 October | 21 |
| 1957 | 14 April | 28 April | 14 | 06 October | 27 October | 21 |
| 1958 | 20 April | 27 April | 7 | 05 October | 26 October | 21 |
| 1959 | 19 April | 26 April | 7 | 04 October | 25 October | 21 |
| 1960 | 10 April | 24 April | 14 | 02 October | 30 October | 28 |
| 1961 | 26 March | 30 April | 35 | 29 October | 29 October | 0 |
| 1962 | 25 March | 29 April | 35 | 28 October | 28 October | 0 |
| 1963 | 31 March | 28 April | 28 | 27 October | 27 October | 0 |
| 1964 | 22 March | 26 April | 35 | 25 October | 25 October | 0 |
| 1965 | 21 March | 25 April | 35 | 24 October | 31 October | 7 |
| 1966 | 20 March | 24 April | 35 | 23 October | 30 October | 7 |
| 1967 | 19 March | 30 April | 42 | 29 October | 29 October | 0 |
| 1968 | 18 February | 28 April | 70 | 27 October | 27 October | 0 |
| 1972 | 19 March | 30 April | 42 | 29 October | 29 October | 0 |
| 1973 | 18 March | 29 April | 42 | 28 October | 28 October | 0 |
| 1974 | 17 March | 06 January | -69 | 27 October | 27 October | 0 |
| 1975 | 16 March | 23 February | -20 | 26 October | 26 October | 0 |
| 1976 | 21 March | 25 April | 35 | 24 October | 31 October | 7 |
| 1977 | 20 March | 24 April | 35 | 23 October | 30 October | 7 |
| 1978 | 19 March | 30 April | 42 | 29 October | 29 October | 0 |
| 1979 | 18 March | 29 April | 42 | 28 October | 28 October | 0 |
| 1980 | 16 March | 27 April | 42 | 26 October | 26 October | 0 |
| 1981 | 29 March | 26 April | 28 | 25 October | 25 October | 0 |
| 1982 | 28 March | 25 April | 28 | 24 October | 31 October | 7 |
| 1983 | 27 March | 24 April | 28 | 23 October | 30 October | 7 |
| 1984 | 25 March | 29 April | 35 | 28 October | 28 October | 0 |
| 1985 | 31 March | 28 April | 28 | 27 October | 27 October | 0 |
| 1986 | 30 March | 27 April | 28 | 26 October | 26 October | 0 |
| 1987 | 29 March | 05 April | 7 | 25 October | 25 October | 0 |
| 1988 | 27 March | 03 April | 7 | 23 October | 30 October | 7 |
| 1989 | 26 March | 02 April | 7 | 29 October | 29 October | 0 |
| 1990 | 25 March | 01 April | 7 | 28 October | 28 October | 0 |
| 1991 | 31 March | 07 April | 7 | 27 October | 27 October | 0 |
| 1992 | 29 March | 05 April | 7 | 25 October | 25 October | 0 |
| 1993 | 28 March | 04 April | 7 | 24 October | 31 October | 7 |
| 1994 | 27 March | 03 April | 7 | 23 October | 30 October | 7 |
| 1995 | 26 March | 02 April | 7 | 22 October | 29 October | 7 |
| 1996 | 31 March | 07 April | 7 | 27 October | 27 October | 0 |
| 1997 | 30 March | 06 April | 7 | 26 October | 26 October | 0 |
| 1998 | 29 March | 05 April | 7 | 25 October | 25 October | 0 |
| 1999 | 28 March | 04 April | 7 | 31 October | 31 October | 0 |
| 2000 | 26 March | 02 April | 7 | 29 October | 29 October | 0 |
| 2001 | 25 March | 01 April | 7 | 28 October | 28 October | 0 |
| 2002 | 31 March | 07 April | 7 | 27 October | 27 October | 0 |
| 2003 | 30 March | 06 April | 7 | 26 October | 26 October | 0 |
| 2004 | 28 March | 04 April | 7 | 31 October | 31 October | 0 |
| 2005 | 27 March | 03 April | 7 | 30 October | 30 October | 0 |
| 2006 | 26 March | 02 April | 7 | 29 October | 29 October | 0 |
| 2007 | 25 March | 11 March | -13 | 28 October | 04 November | 7 |
| 2008 | 30 March | 09 March | -20 | 26 October | 02 November | 7 |
| 2009 | 29 March | 08 March | -20 | 25 October | 01 November | 7 |
| 2010 | 28 March | 14 March | -13 | 31 October | 07 November | 7 |
| 2011 | 27 March | 13 March | -13 | 30 October | 06 November | 7 |
| 2012 | 25 March | 11 March | -13 | 28 October | 04 November | 7 |
| 2013 | 31 March | 10 March | -20 | 27 October | 03 November | 7 |
| 2014 | 30 March | 09 March | -20 | 26 October | 02 November | 7 |
| 2015 | 29 March | 08 March | -20 | 25 October | 01 November | 7 |
| 2016 | 27 March | 13 March | -13 | 30 October | 06 November | 7 |
| 2017 | 26 March | 12 March | -13 | 29 October | 05 November | 7 |
| 2018 | 25 March | 11 March | -13 | 28 October | 04 November | 7 |
| 2019 | 31 March | 10 March | -20 | 27 October | 03 November | 7 |
| 2020 | 29 March | 08 March | -20 | 25 October | 01 November | 7 |
| 2021 | 28 March | 14 March | -13 | 31 October | 07 November | 7 |
| 2022 | 27 March | 13 March | -13 | 30 October | 06 November | 7 |
| 2023 | 26 March | 12 March | -13 | 29 October | 05 November | 7 |
| 2024 | 31 March | 10 March | -20 | 27 October | 03 November | 7 |
| 2025 | 30 March | 09 March | -20 | 26 October | 02 November | 7 |
| 2026 | 29 March | 08 March | -20 | 25 October | 01 November | 7 |
| 2027 | 28 March | 14 March | -13 | 31 October | 07 November | 7 |
| 2028 | 26 March | 12 March | -13 | 29 October | 05 November | 7 |
+------+---------------------+------------------------+--------------------+---------------------+------------------------+--------------------+