The Jewish Calendar

The Jewish calendar is lunisolar. The years are counted according to the Earth's rotation around the Sun, while the Moon's motions are taken into account when determining the months.

On 10 September 2018 (according to the Jewish calendar, on the 1st of Tishrei), the 5779th Jewish year began. This is a conventional calculation based on biblical history. Its starting point is the creation of the world and, more specifically, the day on which Adam and Eve were created. The Bible does not give any dates, but often there is information on how long a given person lived or how old they were when they became a parent. This provided the basis for the estimated calculations of the years.

An interesting fact is that the month of Tishrei, in which the Rosh Hashanah festival is celebrated (literally meaning the "head of the year"), is not the first month in the Jewish calendar at all. Months are not named in the Torah (their names appear later), but they are numbered and the spring month of Nisan is described as the first, while Tishrei is the seventh month.

In the Jewish calendar, months are measured according to the cycles of the Moon and last 29 or 30 days. The birth of a new moon (Rosh Chodesh – literally the "head of the month") has the status of a half-holiday and is accompanied by additional prayers. The full moon always falls on the middle of the month.

However, measuring time only according to the cycles of the moon would mean that the same months, and thus the holidays, would fall on different seasons of the year. Meanwhile, some Jewish holidays are also agricultural in their nature, and in antiquity this was associated with the duty to go on a pilgrimage to the Temple in Jerusalem in order to make a sacrifice from the harvest. It was, therefore, necessary to introduce leap years, which would even out the annual cycle of the full circulation of the Earth around the Sun.

The Jewish leap year is called shana meuberet in Hebrew, which literally means "pregnant year" (in Hebrew, the word shana – "year" is feminine, so it does not sound as awkward as its translation into English). The last month (Adar) is then celebrated twice, one after the other, so there are thirteen months instead of twelve. Interestingly, it is not the second, repeated Adar but the one which falls first that is considered as an additional month. The Purim festival, which falls this month in leap years, is celebrated in its full extent during Adar II, while the same day of Adar I is only treated as a half-holiday.

The Shana Meuberet usually falls on every third year (sometimes every second). During a 19-year cycle, the leap year occurs 7 times (it is the 3rd, 6th, 8th, 11th, 14th, 17th and 19th year). The use of 19-year cycles to synchronize the solar and lunar calendar called the Metonic cycle (from the name of a Greek astronomer from the 5th century BC), is not unique to the Hebrew calendar; the situation was similar, inter alia, in the case of the old, lunisolar Chinese calendar. 19 solar years and 235 lunar months are exactly the same number of days – 6940. The difference is just 2 hours. Therefore, the Jewish calendar diverges from the solar one by 1 day over a span of 216 years.

The names of the Jewish months are not originally Hebrew. They were adapted from the Babylonian calendar after the Jews returned from captivity.

In the table below, the months, along with the holidays falling on them, are listed in accordance with the civil calendar (starting with the month of Tishrei), and not the ecclesiastical one (with Nisan).

A week is an unusual unit of time because, unlike the others, it finds no justification in natural phenomena. Its only source is the Bible. According to the story of God creating the world in 6 days and resting on the seventh day, for Jews, the seventh day of the week – the Shabbat, during which one should abstain from all work, is the Saturday. The Israeli weekend starts on Thursday after work and continues until the end of the Shabbat; Sunday is a working day, the first day of the new week.

In Hebrew, Shabbat is the only day that has its own name. The remaining days have only sequence numbers: the first day (Sunday), the second day, the third day, etc.

However, the moment when the Shabbat or any other day ends is not midnight or any other regular time. "And there was evening and there was morning, one day"^[1] – says Genesis. The same is repeated in the description of each subsequent day of the creation of the world. First the evening, then the day. Therefore, for Jews, a new day begins with the sunset. In the case of the Shabbat and other important holidays, an hour is added (18 minutes before the sunset on Friday and 42 minutes after the holiday). In the summer, it is late evening but in the winter it can be an early-afternoon hour. At that time, many religious owners of shops or restaurants open their places, having no complaints about the lack of customers.

In all printed Jewish calendars, as well as on websites devoted to holidays, one of the most important pieces of information is the exact time of the start and end of the Shabbat, which depends not only on the date but also on the geographical latitude. In Poland, the main cities that have larger Jewish communities, such as Warsaw, Krakow or Wrocław, are accounted for. 

The same applies to the so-called halachic hour ( shaa zmanit ). It is a unit used only for religious purposes (determining the time of prayer, etc.) It is the twelfth part of the day (between sunrise and sunset), and hence, its length varies throughout the year. Each of the three daily prayers of Judaism – the morning (shacharit), the afternoon (mincha) and the evening (maariv) – should be read at a certain time. Taking into account the length of the halachic hour on a particular day, the Jewish calendar specifies the earliest and the latest time when a given prayer, or even its individual components, may be said.

For a worshipper of Judaism, who, in the backlog of everyday affairs, would not want to forget about their religious duties, in the past, this was probably more complicated and required more attention. Today, the Internet is helpful in this regard. There are a lot of pages where someone may enter their location and check all the important times and the length of the halachic hour, and on portable devices it is possible to install an application that sends reminders for any approaching prayer times, the need to light candles before the holiday or say all the blessings that are related to time.

Written by: Julia Makosz,

This work is licensed under a Creative Commons Attribution 3.0 Poland License.