Calendar essentials!

Our current "world" civil calendar, January to December, is called the "Gregorian Calendar". You may know that, but do you know why, and how it works? But YHWH's appointed times are on HIS calendar, the Hebrew Calendar! Do you know anything about the Hebrew Calendar? This short article may help.

The solar year, known as the "tropical year", is the time it takes the earth to go one time around the sun - as seen from the earth. But the tropical year is not a "whole number" of days long! In fact, the tropical year is about 365.2422 days long! However, the calendar must use whole days and that number must be 365. But since 365 full days is about 1/4 of a day shy of the tropical year, every 4 years, the calendar must include a 366th day. Here's why:

4 Tropical years adds up to: 365.2422 + 365.2422 + 365.2422 + 365.2422 = 1460.968 days


4 years of 365 whole days adds up to: 365 + 365 + 365 + 365 = 1460 days

So we see, the total of four, 365-day years is 0.968 days short of four Tropical years - almost one full day short - so the calendar needs a "366th day" in one of those 4 years to stay "in-sync" with the tropical year. You already know this as a "leap year" - that is the one year in every four which includes "February 29th" and has 366 days instead of 365. The added day is called the "leap day". By adding this "leap year", the calendar, instead of being a "fixed" 365 days long, year after year, instead "averages" to be 365.25 days long. (Think about it: 365 + 365 + 365 + 366 divided by 4 is 365.25! The Gregorian calendar is a little better than this, but we'll talk about that later.)

The previous calendar to the current Gregorian was the "Julian Calendar", and is pretty much the same as the Gregorian, but it had a serious problem which the Gregorian corrected. In the Julian calendar, a "leap year" was rigidly applied, every 4 years. So the Julian Calendar averaged exactly 365.25 days long. But that average, since it is a little bit LONGER than the tropical year, gradually gets "ahead" of the sun! The year would slowly "gain" a whole day! In fact, it takes only 128 years for the Julian Calendar to gain that whole day and get ahead of the tropical year!

Here is the math:

365.25 days/year minus 365.2422 days/year = 0.0078 days/year. Seems very tiny doesn't it? The Julian year is only 0.0078 days longer than the year by the sun! So how long will it take to "accumulate" one whole day?

1 day divided by 0.0078 days/year = 128.2 years!

It takes only 2 lifetimes for the Julian Calendar to gain a whole day! This is not a big deal to one person's lifetime, or even 2, but what happens, is this: As the days accumulate, the Calendar starts to get noticeably "off" from the seasons! And that becomes a problem for later generations.

The Julian Calendar came into use in 45 BCE - (about 2060 years ago!), and by the year 325 CE (about 370 years after the Julian Calendar began), the year of the Council of Nicaea, they already were concerned because the Julian Calendar had already added almost 3 days, and that means they could already tell the seasons were not beginning on the days they should! In a long and obscure passing of the Roman Empire, and rise in dominance of Catholicism, the flawed Julian Calendar was finally changed by Pope Gregory XIII - in the late 1500's - when the calendar was already off by 10 days just since the Council of Nicaea!

It was by the Pope's decree that on the 4th of October, 1582 (Julian Calendar), the next day became the "15th of October, 1582" (Gregorian Calendar)!

In other words, by 1582, the old Julian Calendar had gained 10 days since the Council of Nicaea had "decided" Spring should be "March 21st", so they "dropped" the 10 gained days making the next day the "15th", and thus moved the start of Spring back to "March 21st". (Note: When the "days" were "dropped" in 1582, the date changed, but NOT the day of the week! So "Thursday" that week, was still followed by "Friday". Note also, the whole world did not change calendars on that same date in 1582! It actually took the whole world another 347 years to convert to the Gregorian system - all the way up to 1929!)

Now, about why the Gregorian Calendar is better than the old Julian: Remember, the Julian added a day every fourth year, regularly, thus gaining 1 day every 128 years. The idea of the Gregorian Calendar is to do the same thing, but "skip", or omit, adding a day 3 times in 400 years. This makes the Gregorian calendar year average 365.2425 - slightly shorter than the average Julian year, and much closer to the tropical year of 365.2422 days. But since the Gregorian average year is still a little tiny bit greater than the Tropical Year, so it still gains days just like the Julian, but much more slowly. The Gregorian gains only 1 day, in about 3,300 years! (You can do the math!)

So the Gregorian calendar is still not "perfect", indeed, no calendar can be perfect, since ALL calendars must have an intercalary system (i.e. days added to the calendar) to attempt to keep the seasons where we all know them. In fact, though the Spring Equinox was on March 21st in the early years of the 1900's, in our time (~ 2013), the Spring Equinox now falls mostly on March 20th. By the end of this century, the Spring Equinox will often fall on March 19th! Then, in the year 2100, another leap year will be omitted, and the Spring Equinox will "shift" back to March 20th. It's a fascinating study, all by itself, learning the details on how the Gregorian Calendar "works"!

So, with this brief background on our calendar and the leap years, let's now transition to the Hebrew Calendar.

The Hebrew calendar has no relation to the Gregorian Calendar except that Equinoxes and Solstices are common between them (actually common to all calendars), so there is necessarily a relationship between the two calendars because of the tropical year! But, most of us, have grown up using only the Gregorian Calendar, and thus we really are only familiar with Gregorian Calendar dates.

When the Hebrew Calendar is first encountered, it is a bit overwhelming! So I intend here to provide the "essence" of the Hebrew Calendar, enough so that perhaps that "daunting" feeling might be minimized. Bear in mind that in the Biblical times, there was no such thing as either the Julian or the Gregorian Calendar, so in what follows, the ONLY reason to compare Hebrew dates to Gregorian dates is to relate to our familiarity with the Gregorian Calendar!

The Hebrew Calendar is a "luni-solar" (or "lunar-solar") calendar meaning it uses both the moon and the sun. The Gregorian and Julian Calendars make no use of the Moon, syncing the date only with the sun, and thus they are "solar calendars". Very briefly, in the Hebrew Calendar, months begin with the New Moon, and the Year begins according to Scripture. In fact, the very word "month" comes from the moon which defines the "month". Let's break down the Hebrew Calendar so you can get a "feel" for how the Hebrew Calendar works:

Months: There are 12 "New Moons" in one tropical year. In other words, the moon fades and "reappears" 12 times in one solar year, so the Hebrew Calendar has 12 months as the "standard" year. (Indeed, this is also why most all calendars have 12 months in the year - the "original" year was likely "12 moons"!) Recognize also, that there is no reason whatsoever to say there are "12 moons" in a "year" if you did not already understand that the "year" is determined by the sun in its full "circuit" through the constellations.

But the moon orbits the earth in 29 1/2 days (on average), so Hebrew months, again as a "standard", simply alternate months of 29 and 30 days long. This handily accounts for that extra "1/2 day" of the average lunar month which is exceeds 29 "whole" days. Note: My use of the word "standard" is simply descriptive. There is no "official" meaning of the term "standard year" in the Hebrew calendar.

The 12 Hebrew months are: Nisan, Iyyar, Sivan, Tammuz, Av, Elul, Tishri, Cheshvan, Kislev, Tevet, Shevat, Adar. (All these months may be spelled differently than presented here. Please don't get hung-up on that, after all, these are just a phonetic spelling in English of the Hebrew words for these months.) These months do not correlate to "January" to "December". Note: Though any Hebrew month can be 29 days or 30 days, since the length of any month depends entirely on the moon, the modern Hebrew (Jewish) calendar "fixes" the number of days in Nisan, Sivan, Av, Tishri, Shevat to 30, while Iyyar, Tammuz, Elul, and Tevet are 29. The months of Cheshvan, Kislev, and Adar are permitted to have 29 or 30 days as needed. This "fixing" of the number of days in the months sometimes causes today's Hebrew Calendar to fail to follow the moon as it originally did (and should).

Year: Unlike the Gregorian Calendar, which pretty tightly keeps the calendar dates in-sync with the sun (as already mentioned, the Gregorian Calendar fixes the Spring Equinox around March 21st), the Hebrew Calendar year is based on a command from YHWH, and it is the "month" of spring which is more important than the "day" the tropical year begins. So the Hebrew year begins with Nisan - the month of Spring. This is because YHWH changed the start of the year to the month the exodus began. See Exodus 12:2 "You are to begin your calendar with this month; it will be the first month of the year for you." Further, YHWH said: "Observe the month of Spring, and keep Pesach to ADONAI your God; for in the month of Spring, ADONAI your God brought you out of Egypt at night." (Deuteronomy 16:1). It is this second command which fixes the month of Spring and fixes Passover to Spring.

The time of year Passover is kept is important, as it is decreed in Deuteronomy 16:6 as "...the Pesach offering, in the afternoon, as the sun is descending, at the time of year that you came out of Egypt." (Note the scriptures do not say anything about waiting for barley to ripen. Some Bibles, in Deuteronomy 16:1, say "month of Abib" instead of "month of spring", implying a "named month". (Abib was the original name for the month of Nisan.) But the context of the original Hebrew text of Deuteronomy is clear that it meant "month of spring" and not the "month named Abib". So it is important to understand that the calendar is tied to Spring and not to "ripening of barely". We know even in Noah's day, they already well understood the seasons, and the equinoxes and solstices. Genesis 8:22 says "So long as the earth exists, sowing time and harvest, cold and heat, summer and winter, and day and night will not cease." Our modern words for "sowing time and harvest" are the "Equinoxes" (Spring and Fall), and for "summer and winter" we know these as the "Solstices".

Thus the Hebrew year begins with the New Moon of Nisan, and not on a particular day by the sun. And Nisan is kept as the "month of Spring". This is an important concept to understand! In the Gregorian Calendar, the "Year" is fixed by a position of the sun, and the Moon can be "new" on any day of the month! You can say the "moon floats" in the Gregorian Calendar. In the Hebrew Calendar, "Months" are fixed by the Moon, while the sun "floats". Which brings us to...

A complication!

We encounter a complication in the Hebrew Calendar because 12 (lunar) months only has 354 days! (29.5 x 12 = 354). This is 11 days short of the tropical year of 365 days. What to do? Well, for the first couple of years, you can "let it go", so at the end of the 2nd year, the lunar calendar is "off" the solar year by 22 days. Then in the 3rd year, you can insert another month so the 3rd year becomes 384 days. Therefore, at the end of the 3rd year, the Hebrew Calendar is now only 3 days "off" the solar year over the whole 3 years. Follow? Here is a side-by-side comparison to illustrate:

Three Tropical years: 365 + 365 + 365 = 1095 days

Three Hebrew years: 354 + 354 + 384 = 1092 days

Now, if you are savvy, you realize that regularly adding an extra month every 3rd year is not enough to keep in-sync with the Tropical Year. After all, in the first 3-years the calendar is off by 3 days, then in the next 3 years it's off by 6 days (actualy 7 days - left as an exercise for the reader), and so on. This is an astute observation! What to do?

You carefully track the total number of days in the lunar year and the Tropical year, and as the Hebrew Year gets further behind the Tropical Year, you find that sometimes, though not often, it's the 2nd year which needs the extra month instead of the 3rd year! Thus the Hebrew Calendar inserts (intercalates) a "leap month" every 3rd year, but sometimes the 2nd year (but never both the 2nd and 3rd year in a row). In this way, Nisan remains the "month of spring", and the most important day, Pesach (Passover), will always fall on or after the Spring Equinox.

In the familiar Gregorian Calendar leap year, the "extra day" is added in February (and not the 29th! - See "End notes".) In the Hebrew Calendar, the "leap month" is added just before Adar, the last month of the year, so the "Leap Month" becomes "Adar I" and Adar becomes "Adar II" or "Ve'Adar" (literally meaning "and Adar"!)

Thus, because an entire month is sometimes added, it seems that Hebrew Calendar dates "move around". They really don't. It's a perception problem. Think about this: If you had never heard of the Gregorian Calendar, and had grown up instead with the Hebrew calendar, the Hebrew Calendar would seem as natural to you as does the Gregorian! You would know that when the moon grew old, the next month was coming soon, and you knew which was the next month, by name, and you knew which dates in each month were the important dates, and you would simply conduct your life around the Hebrew Calendar! You would never say: "this event is not on the same day as it was last year"! That concept would not occur to you, remember, no "Gregorian Calendar" existed in Bible times! You would even know your birthday as a Hebrew date! Your birthday would always be the same Hebrew Date, and it would not bother you in the least that your birthday simply was never on the same SOLAR day each year, because in the Hebrew Calendar, the solar day does not matter! If you were born in a leap year on say, "12 Adar II", and the current year is not a leap year (and consequently no "Adar II"), you still celebrate your birthday on "12 Adar", because that "completes" the "year" for you in the Hebrew Calendar! This is no different than someone whose birthday in our time is on February 29th! In every non-leap year, they simply celebrate on February 28th (or March 1st if they desire)!

Thus Hebrew dates are Hebrew dates and not to be confused with Gregorian dates. But because we are so intimately tied to the Gregorian Calendar, and so unfamiliar with the Hebrew Calendar, we always see the Hebrew dates given in terms of when they fall on the Gregorian Calendar a particular year! This is what makes it seem that Hebrew dates "move around" and causes no end of confusion, because by the Gregorian Calendar, Hebrew special days are always on different dates each Gregorian year! But it is what it is, so instead, we really should understand both calendars! For example, the Jewish celebration of Hanukkah is the eight days beginning always the 25th of Kislev. But since that time in the Hebrew Calendar typically falls in December, the celebration has unfortunately and incorrectly become associated with "Christmas". (Since Hanukkah's origins precede the birth of the Messiah, and "Dec 25th" is the wrong date of the birth of the Messiah anyway, this is very unfortunate indeed.) At least now hopefully you get the old joke: "Hey, when is Hanukkah this year? It's the 25th of Kislev!"

So it is hoped that this short summary of the Hebrew Calendar has helped reduce some confusion. Just know that Hebrew holidays (historical observances, feasts, Holy Days, etc.) are on FIXED days of the Hebrew Calendar, and that since the Hebrew Calendar is "luni-solar", the Hebrew "year" is by a New Moon, the New Moon of Nisan, "synced" to Spring, and not by what particular day of the "Tropical year" it is. Finally, recognize that since the purposes of two calendars are very different, as believers in YHWH and the Messiah, it is in the Hebrew Calendar where we find the Appointed Times, and not the Gregorian Calendar! After all, when the Messiah walked the earth, it was the Hebrew Calendar He knew and followed! And last time I checked, the Messiah was a bit more important than Pope Gregory XIII!

So there you have it - a brief introduction to the Hebrew Calendar. Yes, there are issues. The method of determining the "new moon" causes much grief. The determination of which new moon is the new moon for Nisan causes grief and dissension. Nowhere in scripture does YHWH ever tell us exactly how to keep the calendar, but He does tell us to "keep Passover", and Sukkot, and Yom Teruah, and Yom Kippur, and Shavuot, and Shabbat while He never said to "observe Christmas" or "paint eggs". Or that "all we have to do is 'believe', and willfully ignore the Appointed Times".

End notes:

Tropical Year:

As mentioned, the Tropical Year is "as seen from the earth". One might say, "Well, what other ways is there to see it?" There are many different ways to "measure" the year! As measured against the fixed stars, the "year" is actually about 20 minutes longer than the Tropical Year! Even the Tropical Year itself is slightly longer or shorter if you are measuring it from an equinox, or from an apside (earth's far point or close point to the sun)! To keep this article short (!), I chose to use the average Tropical Year, which is 365.2422 days - though even that number changes ever so slightly year to year!

The Gregorian Calendar "Leap Day":

I mentioned that the Leap Day in the Gregorian Calendar is not February 29th. It's true! When the leap year was introduced, in 45 BCE, the added day was added before (what we call today) "February 24th". This is because of the way the old Roman calendar named days - they did not number them sequentially as we do. To make a long and fascinating story very brief, the "1st day" of any month was not the "1st day", it was instead called the "Kalendae" of the month. (For example, what we would call "March 1st", the Romans would say "Kalendae of March".) When Julius Caesar was implementing his calendar in 45 BCE, he declared the "6th day before the Kalendae of March" would be "doubled"! Now, the Romans did not have a "2nd day before" the Kalendae of any month (strange but true!), so by the way they counted, the "6th day before" was what we today call the "24th"! So the "leap day" was added the "6th day before the Kalnedae of March", and they literally had two days in a row called the "6th day before the Kalendae of March"! In the Gregorian Calendar, this would be like counting the leap day this way: Feb 22nd, 23rd, 24th, 24th, 25th, 26th, 27th, 28th. (See - "Feb 24th" was doubled!) But we don't number days that way, so in our case, each day beyond Feb 24th is simply incremented, and we end up with a "Feb 29th" in the leap year! Nevertheless, technically, the leap day is "Feb 24th", and not "Feb 29th"! For fascinating reading please see the "Calendar FAQ" kept by Claus T??ndering, in particular, the page on the Roman calendar at

The New Moon:

This article did not discuss HOW the month begins with the New Moon. Though some will argue that "sighting the crescent" is an "easy and sure" way to determine the new month. It is "easy", but completely wrong. It is wrong, in the simplest terms, because the first visibility of a new crescent is never the same from month to month! No calendar would (or should) rely on a mechanism which has an unsure "start" day for up to 3 days! So how should the new month be determined if it is not the visible crescent?

In short, without the aid of calculation, you simply watch the old moon! The old moon is also visible as a thin crescent on the last days of the month but visible before sunrise. And after observing how the old moon looks as it changes throughout the year, you have a reliable marker of when the conjunction happens - even though you can't see the conjunction - and then you know which sunset becomes the 1st day of the new month. If the new crescent is visible that night, at sunset, which it sometimes is, then you are blessed by it. But more often than not, the new crescent is not seen till the 1st day is ending, i.e., the 2nd day is beginning. This means the new crescent can only be a backward marker indicating that the month has already begun. Today, it is far easier to calculate the time of conjunction than it is to watch the moon each day since we can very accurately calculate the time of the conjunction and immediately know which sunset following conjunction is the 1st day of the new month. The downside is that people have mostly forgotten how to watch the moon throughout the whole month, and they have forgotten the usefulness of the many signs it provides.

Date of Passover:

The date of Passover is absolutely key. You get Passover wrong, and all the other Holy Days of the year will be wrong. As pointed out above in the main body of this article, YHWH set the start of the year to the month the exodus began - Nisan. Further, YHWH established that Passover was in the month of Spring, and that Spring was the time they came out of Egypt. And what's more, not only is the time of year important, but the very day is important! Deuteronomy 16:6 records: "...[prepare] the pesach-offering, in the afternoon, when the sun descends, the appointed of your departure from Egypt." And from Exodus 12, we know that Passover itself comes in the mid/late afternoon the 14th of the month. Thus, Passover offering falls "in the month of Spring", the afternoon the day of the month changes to the 15th. A day, in fact, if your calendar is right, a full moon or nearly full moon will rise at sunset!

We know the Hebrew Calendar is not established by the sun in the way we do today. Rather, as Josephus explained, the 14th had to fall when the "sun is in Aries". The term "sun is in Aries" was a term for the Spring Equinox. "Spring" was not so much a "day" as it was a "transition" with a beginning. We know Josephus understood that the "Sun in Aries" marked "spring" in the time of Moses because by the time of Josephus, due to precession of the equinoxes, the Spring Equinox did not happen when the "sun was in Aries", rather, Josephus was reporting on the "condition" which established the 14th of Nisan! In other words, in the time of Moses, Spring began when the "sun was in Aries" as this described the Spring Equinox. But today, we know the "Spring Equinox" (Vernal Equinox) itself defines the event, regardless of the background constellation the sun happens to be "in". So today, by stating the rule as: "The New Moon nearest Spring Equinox is Nisan, and sunset the 14th of Nisan is Passover"- we are completely consistent with the historical determination of Passover, and this keeps Passover in the right time.

Hebrew Calendar Variations:

I must mention the differences in some of the various Hebrew Calendars. Again, all of these variations cannot be thoroughly explained here as it is way beyond the scope of this article.