Most dates are open. Four stretches of the Jewish calendar are the ones officiants turn down.

You picked a Saturday in May because the venue had it and your cousin can fly in, and the second rabbi you emailed said she couldn't do that weekend without saying why. Nothing is wrong with your date. There's a second calendar running underneath the civil one, and it's worth seeing the shape of it before the deposit clears.

Which dates can't you get married on?

Four stretches, and the rest of the year is open. Shabbat (the Jewish sabbath) every week, the major festivals, most of the Omer (a seven-week period in spring), and the Three Weeks (a mourning period in midsummer). That's the entire list. How much of it applies to you depends on who's officiating, which is the part most couples don't hear until after they've booked.

• Shabbat, the Jewish sabbath, from sundown Friday to sundown Saturday, every week of the year.
• The major festivals: Rosh Hashanah (the Jewish new year), Yom Kippur (the day of atonement), Sukkot (the autumn festival of booths), Passover, and Shavuot (the festival seven weeks after Passover), plus the days attached to them.
• The Omer, the seven weeks counted from Passover to Shavuot, usually landing between April and early June. One day in the middle, Lag BaOmer (the thirty-third day of the count), is a traditional exception and a popular wedding date because of it.
• The Three Weeks, a midsummer stretch that usually falls in July and ends on Tisha B'Av, a fast day marking the destruction of the Temples in Jerusalem.

Why do these restrictions exist?

Different reasons for different dates, and none of them are about you. A wedding is understood as a legal act, and traditional practice keeps legal acts off Shabbat and festival days, which are set apart from ordinary business. There's also a principle that you don't fold one celebration into another, so a festival keeps its own joy and a wedding gets a day of its own. The Omer and the Three Weeks work differently: both are periods of mourning on the Jewish calendar, and celebrations are held back during them.

The Omer's mourning is traditionally tied to a plague that killed the students of Rabbi Akiva in the second century. The Three Weeks mark the siege and destruction of the Temples in Jerusalem, which is why the stretch closes on a fast day rather than a feast. Neither has anything to do with whether a marriage is a good idea in spring.

Do all rabbis observe them?

No, and this is the part that changes your search. Reform practice commonly disregards the Omer and the Three Weeks, so a Reform rabbi is often free on a Sunday in May that a Conservative colleague would decline. Conservative and Orthodox rabbis generally observe all four. Independent officiants set their own practice, and cantors vary the same way rabbis do.

Shabbat is the closest thing to universal, and even there the restriction is about hours rather than the day. None of this makes one officiant more serious than another. These are different communities keeping different practices, and they have been for a very long time. Your job isn't to work out who's right. It's to find out who's available.

What if your date falls on one?

You have four options and none of them involve moving the wedding. If the conflict is Shabbat or a festival day, hold the ceremony after sundown. If it's the Omer or the Three Weeks, hire an officiant whose practice doesn't include that restriction, which is a large share of them. Or sign the license civilly on a different day and hold the Jewish ceremony whenever you like, or simply book the person who says yes to the date you already have.

Nobody here is going to tell you your date is wrong. The date is yours, and a wedding on it is a Jewish wedding. What changes is the size of the group of officiants who'll stand under the chuppah (the canopy a couple stands under) with you on that day, which is a filtering problem and not a verdict. Finding a rabbi outside a synagogue covers where those people are. In a city like Chicago, the list of officiants working there runs into the dozens, and their calendars are not identical.

How do you check a specific date?

Look up the Hebrew date your civil date falls on, then send it to an officiant. The Jewish calendar is lunar with adjustments, so it slides against the civil one every year: a Sunday in mid-May can sit inside the Omer one year and be clear of it the next. Any free Hebrew date converter will tell you in a few seconds. Then ask the officiant directly, giving the date and the ceremony hour together, because those two facts are what they're really answering.

Do this before you talk about anything else. An officiant can say yes or no in one line, and that line saves a three-week email thread about ceremony style with someone who was never available in the first place. The other questions worth asking early belong in the same message.

Does a Saturday wedding work?

Yes, once Shabbat has ended, which is nightfall rather than sunset and runs roughly 40 to 70 minutes later. In late June in the northern United States that can mean a ceremony starting near 9pm; in December it's about 5:15 at the earliest, and the evening looks entirely ordinary. Most rabbis and cantors who won't officiate during Shabbat will officiate once it ends, and some officiants of every kind will take a Saturday at any hour.

Saturday weddings and Shabbat goes through that timing season by season, because the gap between a June Saturday and a December one is about five hours, and it decides your whole reception.

The one thing worth doing first

Before the venue deposit, send your date and your ceremony time to three officiants and ask one question: can you marry us then? You'll have answers inside a day. Either you're choosing from everybody or you're choosing from a smaller group, and both of those are fine. Not knowing which is the only version that costs you anything.