Timekeeping in ancient Israel.

The calendar most of the planet uses, called either the western calendar or the Gregorian calendar, originated in 1582 when Pope Gregory 13 introduced it as an update of the Roman calendar adopted by Julius Caesar in 45BC. Since Gregory introduced it right after the Protestant split, it took a while before all Protestant countries adopted it. Various Orthodox churches still haven’t adopted it, preferring to stick with Caesar’s calendar, ’cause it’s not Catholic. Meanwhile nations which aren’t even predominantly Christian—’cause of western influences or trade—do use it. As well as their own local calendars. Japan, fr’instance.

Israel likewise uses the western calendar. And its local calendar, the one which predates the western calendar by centuries: The Hebrew calendar.

That’s the calendar we find in the bible. It even predates the Hebrews: It was used all over the ancient middle east, including by the Assyrians and Babylonians who conquered Israel. The Hebrew calendar’s months all have Assyrian names, although a few of the original Canaanite names managed to slip into the bible:

  1. אָבִיב/Avív (“green”), the first month. Ex 12.2, 13.4 Tel Aviv (KJV “Telabib”) in Babylon Ek 3.15 was named for it; Tel Aviv in Israel is named for that.
  2. זִֽו/Ziv (“bright”), the second month. 1Ki 6.1
  3. אֵיתָניִם/Eytaním (“strong ones”), the seventh month. 1Ki 8.2
  4. בּוּל/Bul (“produce”), the eighth month. 1Ki 6.38

Otherwise the months are just called “third month,” “fifth month,” and so forth. We don’t know what their Canaanite names were; they might’ve been named for pagan gods, just like the Roman calendar, so the Hebrews didn’t care to remember them. In any event here are the current names.

ניִסָן/Nisán 30Spring; mid-March to mid-AprilPassover
אִיָּר/Iyyár 29Mid-spring; mid-April to mid-May
סִיוָן/Siván 30Late spring; mid-May to mid-JuneShavuót (Pentecost)
תַּמּוּז/Tammúz 29Summer; mid-June to mid-July
אָב/Av 30Mid-summer; mid-July to mid-August
אֱלוּל/Elúl 29Late summer; mid-August to mid-September
תִּשׁרִי/Tišreí 30Fall; mid-September to mid-OctoberRosh Hashanah, Sukkot
מַרְחֶשְׁוָן/Markhéšvan 29/30Mid-fall; mid-October to mid-November
כִּסְלֵו/Khislév 29/30Late fall; mid-November to mid-DecemberHanukkah
טֵבֶת/Tevét 29Winter; mid-December to mid-January
שְׁבָט/Ševát 30Mid-winter; mid-January to mid-February
אֲדָר/Adár 29/30Late winter; mid-February to mid-MarchPurim

The year, in the Old Testament, was determined by how long the current king had ruled: It’s “the seventh year of King David” or something like that. Not practical at all when you’re trying to determine events which happened centuries ago; you gotta know how long ago, and how long, David ruled. And we actually don’t. Scholars have tried adding up all the reigns, much like they’ve tried adding up the ages in genealogies, but you still won’t get exact dates that way; it doesn’t take into account kings whose reigns overlap, or the fact the bible sometimes rounds the numbers. We figure David reigned was near the end of the 10th century BC, but good luck pinpointing the year. Not that various scholars don’t try… but we honestly don’t have any dates pinpointed till the bible starts mentioning Babylonian kings.

So where’d the Hebrew years come from? Medieval rabbis. They estimated God created the universe on 1 Tišrei 3761BC, and have been counting up since then. (Yep, even sooner than the 4004BCE which young-earth creationists prefer; go figure.) So this means today is the in the Hebrew calendar, according to Hebcal.com.

New moons and blood moons.

The Hebrew months are lunar, which means every month begins on the new moon. That’s why months vary between 29 and 30 days, instead of the western calendar’s 30 and 31 days: It’s synced with the moon.

As a result the Hebrew year comes out to between 354 and 356 days. Which, y’notice, doesn’t quite line up with the earth’s 365¼-day trip round the sun. So what keeps their calendar from sliding around the seasons like the Muslim calendar? Simple: The Hebrew calendar has a leap month. If the year ends and it’s not yet spring, they add a month. The leap month is called Adár Aléf/“Adár A,” or Adár Rishón/“First Adár.” Followed, of course, by the usual Adár—which is called Adár Bet/“Adár B,” or Adár Šení/“Second Adár.” Syncing it up with the seasons therefore makes it a lunisolar calendar.

Since lunar eclipses only happen on new moons, various “prophecy scholars” try to make a big deal about how various “blood moons” coincide with significant Jewish holidays—like Rosh Hashanah, on 1 Tišreí. Which just goes to show how ignorant they are of how the Hebrew calendar works: Of course blood moons coincide with Jewish holidays. It’s a lunar calendar! But like Jesus said, these things don’t mean the End has come. Only that some “prophecy scholar” is trying to peddle books to the fearful.

The ancients used to celebrate new moons, so the Hebrews did too. 2Ch 2.4 They tried to make them sacred by offering sacrifices to the LORD, although he didn’t actually command ’em to do so. (He did order a sacrifice every month, Nu 28.14 but it’s debatable whether this sacrifice was required on the first day of the month.) But neither did the LORD forbid new-moon celebrations—so long that the Hebrews actually followed him. When they didn’t, he objected to the hypocrisy of such celebrations. Is 1.13-14 Don’t just make a big display at festivals; worship him for real.

I mentioned Rosh Hashanah. That’s רֹאשׁ הַשָּׁנָ֜ה, Hebrew for “head [of the] year”—the Hebrew new year. I know; their calendar goes up a year in the seventh month, not the first like the western calendar. But some western countries used to do the very same thing. For the longest time England used to consider 25 March their new year’s day: 24 March 1700 was directly followed by 25 March 1701. Weird, but that’s what they were used to. Same as Jews are used to the year changing on 1 Tišreí instead of 1 Nisán. Sometimes it’s called the beginning of the secular year… but that’d be inaccurate, because Rosh Hashanah is totally a religious holiday. It’s in the bible. Nu 29.1-6 You blow trumpets, offer sacrifices, take the day off; it’s the first of the High Holy Days.

Hebrew days.

The Hebrew days of the week don’t have names, unlike our Sunday, Monday, etc. There’s “first day,” “second day,” and so on. (Nowadays they’ll sometimes go with “Day A,” “Day B,” etc.) Though in New Testament times, Friday became known as “Preparation,” Mk 15.42 because it was the day you finished your work before Sabbath. Mark also called it “pre-Sabbath” (Greek προσάββατον/prosávvaton), though I’m not sure how widely used that term was, since the other gospels went with Preparation. Arguably “Preparation” was what they called any day before a holiday, but since Sabbath was a weekly holiday, when you said Preparation you meant Friday.

I wrote about Sabbath elsewhere. It’s a weekly holiday, and treated more like a holiday than westerners tend to treat their weekends.

Western days begin at midnight, but middle eastern days began at sunset. So when the sun went down on Friday, it wasn’t Friday night; it was Sabbath. Friday night was last night. I know; it’s a tricky thing for some westerners to wrap their brains around. (Though some of us are up past midnight and already know what it’s like to be awake when the day changes: “Well, earlier today… oh, I mean yesterday; it’s after midnight, isn’t it?”)
Hours in the Roman Empire adjusted with the length of the day. Wikipedia
Some rabbis offered rulings about when precisely the day changed, like how many stars you can see in the sky after the sun goes down. But most folks followed the usual rule of thumb: The sun’s down; it’s tomorrow.

Hours worked a little differently. Hours were based on the length of time between sunrise, noon, and sunset. There were six hours before noon, and six hours after noon. But as you know, the length of a day in June is a bit different from the length of a day in December. So the hours stretched or shrank to fit. The Hebrews didn’t divide the night into hours, but אַשְׁמֻר֑וֹת/ašmurót, “watches”—named for a night guard’s shifts. The ancient Hebrews had three watches, but by New Testament times they’d added a fourth. These watches naturally shifted in length, same as the hours of the day.

I could chart it for you, but remember: If the day’s any longer or shorter (and it usually is), it’s not gonna precisely line up with western time. These are rough estimates. Really rough.

First watchFor three hours after sundown
OT days: For four hours after sundown
6pm to 9pm
OT days: 6pm to 10pm
Second watchThe three hours before midnight
OT days: Four hours in the middle of the night
9pm to 12am
OT days: 10pm to 2am
Third watchThe three hours after midnight
OT days: For four hours before dawn
12am to 3am
OT days: 2am to 6am
Fourth watchThe three hours before dawn
OT days: Didn’t have a fourth watch
3am to 6am
First hourFirst sixth of the morning6am to 7am
Second hourSecond sixth of the morning7am to 8am
Third hourThird sixth of the morning8am to 9am
Fourth hourFourth sixth of the morning9am to 10am
Fifth hourFifth sixth of the morning10am to 11am
Sixth hourLast sixth of the morning, before noon11am to 12pm
Seventh hourFirst sixth after noon12pm to 1pm
Eighth hourSecond sixth of the afternoon1pm to 2pm
Ninth hourThird sixth of the afternoon2pm to 3pm
Tenth hourFourth sixth of the afternoon3pm to 4pm
Eleventh hourFifth sixth of the afternoon4pm to 5pm
Twelfth hourLast sixth of the afternoon, before sundown5pm to 6pm

And since the hours were so flexible, nobody talked in terms of “5:30” or anything like that. Western time wasn’t sorted out for several centuries yet. When the writers of the bible say “it was the sixth hour” or something like that, it was around the sixth hour; they weren’t gonna be as exact as westerners expect. (Just naming the hour at all was pretty darned exact for them.)

Bible background.