The 3-letter root ש.נ.ה has several different meanings but the most common in everyday speech is “year”. A year is the time it takes the Earth to go around the sun. Because this is a natural occurrence, it is known as a natural unit of time. Months (based on the moon) and days (earth’s rotation) are other examples of natural units. Weeks, hours, minutes and seconds are not connected to any natural event and are arbitrary units.
The problem with natural units of time is that they are hard to work with. A year is just over 365 days; around 12 months and 11 days. It is very difficult to synchronise months and years because the relationship is so awkward. In our secular calendar, we use solar years and have given up on trying to link between months and the cycles of the moon. The Muslim calendar is based on lunar months but has lost its link with the sun. Muslim festivals fall in a different season every year. The Jewish calendar maintains a connection with both the sun and the moon – very difficult feat. This is based on a verse in the book of Exodus which refers to the month in which the festival of Passover occurs as חודש האביב [Hodesh HaAviv] – the month of spring, indicating that Hebrew months need to maintain their link both to the moon and to the seasons of the year.
The Hebrew calendar uses some complicated calculations. Months are always connected to the new moon, but in order to stay in sync with the seasons an extra month is added 7 times during a 19-year cycle. The Hebrew year can have either 12 or 13 lunar months. In early times a new month started whenever the new moon was sighted. Today this is a simple calculation; each month has 29 days, 12 hours, and 793 “parts”. [= around 2650 seconds]. Once you know where you are in the 19-year cycle, and whether it is at 12 or 13-month year, you simply add the appropriate number of days, hours and seconds to determine the exact moment when the following New Year will occur.
But it is not so simple. When setting the date of the New Year there are several additional factors that need to be taken into consideration. Sometimes an extra day is added to the year to avoid complications. Although there are several potential difficulties, I will mention the 2 most frequent reasons for adding an extra day.
The first reason for adding a day is known as מולד זקן [Molad Zaken] – an Old Moon. If the precise moment of Rosh Hashanah occurs after midday then an extra day is added. The reason for this is that a New Moon appearing at the end of the day is considered to belong to the next night rather than the night before. This happens about 25% of the time.
The second reason for adding an extra day is when Rosh Hashanah lands at an awkward time. Rosh Hashanah is not allowed to occur on Sunday, Wednesday or Friday. Wednesday and Friday are not allowed because this would cause Yom Kippur to land adjacent to Shabbat. It is almost impossible to observe Shabbat and Yom Kippur without preparation time in-between, and therefore the calendar is engineered to prevent this from happening. The New Year cannot start on a Sunday to prevent Hoshana Raba from landing on Shabbat. Were this to happen it would not be possible to observe the special rituals of Hoshana Raba. This rule means that an extra day is added to a year almost 50% of the time.
Finally, if both of these events occur in the same year, then 2 extra days are added to the calendar!
In short, a year is simply the amount of time it takes for the earth to go around the sun. But calculating when that will be is not a simple thing at all.
Rabbi Chaim Weiner
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