American holidays can be strange things. Many celebrate events, but only a few fall on the actual date of the anniversary of the event. Independence Day is always July 4. Christmas is always December 25 (even though that date really isnít close to the date of the event it is supposed to celebrate). January 1 is always New Yearís Day. February 14 and March 17 are always Valentineís Day and Saint Patrickís Day respectively. Some days are moveable simply because they were originated that way. Thanksgiving is always the fourth Thursday in November, and Motherís Day and Fatherís Day are always on a Sunday in May and June. The formula for Easter was not dictated by Americans, but is a complex calculation based on the full moon and the calendar, sometimes taking it far away from Passover, on which it was based. Then there are the Monday Holidays. Veteranís Day (formerly Armistice Day) used to be on November 11, commemorating the armistice ending World War I. For a while it was moved to the closest Monday, but is again on the designated date. Martin Luther King, Jr.ís birthday is celebrated on a Monday, regardless of the actual birthdate. Labor Day and Memorial Day are now on Mondays, although the latter used to be on a specific date. Sometimes you donít even know if a holiday is a Monday holiday or a specific date holiday. Godís calendar for the Jewish people, on the other hand, seems simple.
Maybe it is simpler because the Jews base their calendar on the moon. The first appearance of the new moon is always Rosh Kodesh (the head of the month). Once a year, interestingly in the seventh month, the new moon signals Rosh haShanah (the head of the year, which is September 4 in 2013). This corresponds with the holiday of the blowing of trumpets (Lev 23:23). When is Trumpets? Easy to remember. It is on Rosh haShanah.
Three major holidays required that Jewish men travel to Jerusalem for their celebration. These are Pesach (Passover), Shavuos (Pentecost), and Succos (the Feast of Booths, September 18 in 2013). All three of these happen to fall on the fifteenth day of their months. The scriptures donít give a reason they should fall on that day, but one can make a reasonable speculation. Since the people had to travel to Jerusalem, and since they did not have rapid transit, the fifteenth of the month would be the best possible day for the holiday. If the month begins with the new moon, the fifteenth is necessarily the full moon. If you are traveling by foot or by donkey, you may want to travel into the night. Going to the holiday, then, you are traveling by the waxing moon, getting brighter each night. Going home, travel would be by the waning moon, beginning with a period of relatively bright moonlight. In the cases of Pesach and Succos, the week-long celebrations would be accompanied by bright evenings. Perhaps with air and automotive travel, these considerations are not as great today, but when travel was more leisurely it may have made a great difference.
If this is the justification for these holidays falling on the middle day of the month, it merely emphasizes Godís care for his people. If he is going to insist on their traveling to one location three times a year, at least he is going to make it as comfortable as possible for them. And as safe as possible, because travel in the dark of the moon can be both physically dangerous and allow cover for those who would rob travelers who are known to be carrying money for the festivals.
Then there is Yom Kippur. It falls on the tenth day of the seventh month (September 13 in 2013). But it is an unusual holiday in many ways. Generally, though, one could say the Jewish holidays were very enlightening.