New York:

zone1.
  offset= {-4, 56, 02}
  ends= {{1883, 11, 18}, {12,03,57}, w}
        or {{1883, 11, 18}, {12,03,57}, s}
        or {{1883, 11, 18}, {16,59,59}, u}


from minimum
  dst= none
  
  % zone change
  end= zone1.ends




zone2.
  offset= {-5,0,0}
  ends= {{1920,1,1}, {0,0,0}, w}


from zone1.ends+1sec
  dst= none
  
  % dst event
  end= {{1918,3,31}, {1,59,59}, w}
       or {{1918,3,31}, {1,59,59}, s}
       or {{1918,3,31}, {6,59,59}, u}


from {{1918,3,31}, {7,0,0}, u}
  dst= {1,0,0}

  % dst event
  end= {{1918,10,27}, {1,59,59}, w}
       or {{1918,10,27}, {0,59,59}, s}
       or {{1918,10,27}, {5,59,59}, u}


from {{1918,10,27}, {6,0,0}, u}
  dst= none

  % dst event
  end= {{1919,3,30}, {1,59,59}, w}
       or {{1919,3,30}, {1,59,59}, s}
       or {{1919,3,30}, {6,59,59}, u}
  

from {{1919,3,30}, {7,0,0}, u}
  dst= {1,0,0}

  % dst event
  end= {{1919,10,26}, {1,59,59}, w}
       or {{1919,10,26}, {0,59,59}, s}
       or {{1919,10,26}, {5,59,59}, u}


from {{1919,10,26}, {5,59,59}, u}
  dst= none

  % zone end
  end= {{1919,12,31}, {23,59,59}, w}
       or {{1919,12,31}, {23,59,59}, s}
       or {{1920,1,1}, {4,59,59}, u}


zone3.
  offset= {-5,0,0}
  ends= {{1942,1,1}, {0,0,0}, w}

from {{1920,1,1}, {5,0,0}, u}
  dst= none %from previous
  


GENERAL PATTERN

in zoneX.
  offset= {HH,MM,SS}
  end= {{Y,M,D},{HH,MM,SS}, w} %% usually wall-time, can be otherwise

from previous.ends +1sec
  dst= previous.dst

  calculate all times for begin (w/s/u)

  foreach rule:
    given begin, current dst and offset,
     - calculate oldest change > begin %% may be none
  nextRule= the rule with the earliest of these dates

  if nextRule.start > zoneX.end:
    end= zoneX.end-1sec
    next_zone (offset & end)
  else:
    end= oldest.time-1sec

  nextDst= nextRule.dst
  nextBegin= end+1sec