We count time in many ways. Much of the world follows the Gregorian calendar, instituted by Pope Gregory XIII in the 16th century, in which years are counted from the assumed year of the birth of Jesus. The Jewish calendar, by contrast, counts time from the year the rabbis thought marked God’s creation of the world, 3,761 years before the Common Era. The Muslim calendar counts from the Hijra, the year 622 CE when Muhammad and his followers moved from Mecca to Medina.
Jews have an implicit awareness of when to count what kinds of times — using the Gregorian date on civil contracts, for example, and using the Hebrew year to mark Rosh Hashanah, the Jewish New Year. This precedent dates to — you guessed it — the Talmud!
A multitude of calendars isn’t just a modern phenomenon. In the rabbis’ day, ancient Romans counted time from the foundation of Rome while much of the eastern Roman and the Sasanian Empires counted time according to the beginning of the Seleucid era (312 BCE). Since contracts needed to be signed, dated and witnessed to be valid, they needed to use the correct date — one recognized and understood by the wider community. The rabbis gave this the force of law. On today’s page, the sage Ulla quotes a mishnah found originally in Gittin 79b:
If a man wrote a bill of divorce and dated it according to a kingdom that is not suitable — to the kingdom of Media or to the kingdom of Greece — or to the building of the Temple or to the destruction of the Temple … she must leave this one and that one.
If a man writes a bill of divorce for his wife but dates it according to the wrong calendar, then the divorce is invalid, and if she has subsequently remarried, her second marriage is also invalid. The stakes for getting dates right are high!
According to the mishnah, using the calendars of Media and Greece in formal contacts invalidates the contract because those kingdoms no longer exist — or, at the very least, no longer set the standard calendar. Counting the years from the beginning or end of the Temple in Jerusalem — though a powerful ideological statement about the Jewish connection to the Temple — was also non-standard. The mishnah does not seem to be opposed to marking time based on the Temple, or even on the kingdoms of Media or Greece. But using those times in legal contexts, because they are non-standard, is inappropriate.
To be a minority in a dominant culture is to constantly live in multiple worlds, worlds that often have different values, social norms and, yes, understandings of how time is organized. Today’s daf recognizes the challenges inherent in this multiplicity. Should we remain insular, counting time using only the Jewish calendar? Should we give up our traditional calendars and adopt that of the majority? Should we create new calendars that reflect new values or moments we want to highlight? No, says this mishnah. Instead, we must understand the legal norms that make certain kinds of calendars valid in particular contexts. While Jewish ritual moments can and should be marked on the Jewish calendar, legally effective contracts must take account of the legal standards of our regions.
So how is a woman to know if her divorce decree is legitimate? After all, the mishnah tells us that getting the year wrong can invalidate a woman’s future marriages. The Gemara concludes:
She should have had the bill of divorce read (by someone who can confirm that the date is correct).
When in doubt, ask!
Read all of Yevamot 91 on Sefaria.