Between Mincha and N'eilah on Yom Kippur (Yom Kippur has 4 services during the day, whereas, there are usually 3. Ne'ilah is the additional service and occurs just before sunset and is the final service of Yom Kippur) Rabbi Ginsburg of Cong. Sons of Israel conducts a 15- 30 min. "Ask the Rabbi" session. Pretty much anything is fair game. People can (and do) ask the rabbi any type of question. Most of the time the rabbi answers them. Occasionally, he is stumped.
This year, someone asked Rabbi Ginsburg why the earliest candle-lighting time of the year is always about two weeks before the shortest day of the year. Rabbi Ginsburg was stumped and knowing that I was researching part of the calendar, he asked me if I would answer the question.
I knew that it had nothing to do with the Judaic calendar and was strictly an astronomical process. Candle lighting always occurs 18 minutes before sunset - whenever that is in your local area. I explained that my best surmise was that it had something to do with how close your location was to the latitude of the time zone change. In other words, Boston, which is further east than New York has an earlier sunset than NYC. Similarly, Detroit's sunset is about 45 minutes to an hour later than NYC. So, this may affect the date of the earliest sunset and candle-lighting time, as well.
During Thanksgiving, I ran this question by Rabbi Grussgott, a close friend of my wife. He had a simpler analysis. He said that the earliest sunset, which is what candle-lighting is based on, does not necessarily mean that this is the shortest day of the year. Now, I figured that he meant that this has something to do with "Sha'ot Z'mani'ot" meaning "seasonal hours".
In brief - the "seasonal hours" concept is used in Judaism in many areas and it defines the latest time for certain prayers. For example, in Judaic Law, the latest time to say the morning prayer, Shacharit is approx. 4 hours of the day. The definition of "day" is not a constant 24 hours, but, rather, is the length of time between sunrise and sunset. Thus, to calculate what 1 hour is, you divide that length by 12. Depending on the time of year, then, an "hour" may be more or less than 60 minutes. That's what's meant by a "seasonal hour".
Regarding candle lighting, the calculation is far simpler than this analysis. As stated, above, candle lighting is a fixed 18 minutes before sunset. So, I looked up the sunrise / sunset table for Woodmere, NY. (You will have to fill in the form with the fields for your state and city.) I noticed that for 2014, the earliest sunset is at 16:28, meaning that candle lighting is 18 minutes earlier at 16:10 (4:10 pm). This occurs on Dec. 1, and stays at this time for about 2 weeks until Dec. 14, when sunset starts to get later.
As sunset stays the same, sunrise gets about 1 minute later each day. So, in fact, the day length is shrinking, indeed. As a matter of fact, on Dec. 1, the start of the earliest sunset whch is 16:28, sunrise is 06:59. On Dec. 20, the start of winter, sunrise is 07:15, while sunset is 16:30. So, in those 2 weeks, while sunset gained just 3 minutes, sunrise gained 15 minutes. And, in fact, Dec. 20 is the shortest day of the year, but not the date with the earliest sunset, which is the only thing that affects candle lighting.
Now, as to why this happens - I have to research further. I surmise the may have something to do with the tilt of the earth's axis, the plane of orbit, and the angle of the sun on the horizon, all of which are probably factors in sunrise and sunset. In short, though, candle lighting time is based on astronomical calculations and, of course, in this case are purely solar, not lunar.
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