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Bo: Months and Dates in Halacha

This month is for you the first of months, it is the first, for you, among the months of the year (Shemos 12:2)

The very first mitzvah that was given to the Jewish people as a nation was the mitzvah of Kiddush Hachodesh: “This month is for you the first of months, it is the first, for you, among the months of the year” (Shemos 12:2). Although the actual mitzvah of setting and sanctifying the month is unfortunately not practiced today, the interpretation that Ramban gives to the text hints to a current application of the mitzvah.

According to Ramban, the verse not only teaches the mitzvah of sanctifying the month, but also teaches us the correct order of the months of the year. The Torah informs us that the month on which we were brought forth from Egypt is the first month of the year, the other months following consecutively. By numbering the months of the year in this method, the calendar itself serves as a means for recollection of Yetzias Mitzrayim.

Based on the teaching of Ramban and later commentaries , some are particular to mention the Hebrew date at the opening of letters and other documents, as well as in everyday affairs. In the following article we will discuss  the halachic requirement of doing so. Is there such an obligation,, or can the secular date suffice?

Numbering the Months of the Year

After stating the basic instruction to number the months of the year after the event of Yetzias Mitzrayim, Ramban addresses the question of the names of the months commonly used today. If there is a mitzvah to number the months of the year in accordance with our redemption from Egypt, why do we use names, instead of numbers?

Ramban begins his answer with an explanation of how this became the common practice.  Although the mitzvah was initially to count the months of the year in accordance with the redemption from Egypt, after the Jews returned from Babylon, they began referring to the months by their Persian names, as we know today.

This, is based on the prophecy in Yirmiyahu: “It will no longer be said, ‘Hashem, who redeemed the Children of Israel from the land of Egypt,’ but rather ‘Hashem, who rescued and brought forth the Children of Israel from the northern land” (Yirmiyahu 16:14-15). Calling the months by their Persian names served to remind the people of their second return to Zion.

The Continuous Mitzvah of Numbering Months

Does this teaching of Ramban mean that the mitzvah of numbering the months no longer applies? This question is the subject of a dispute among authorities.

According to Sefer Ikkrim (maamar 3, chap. 15), the initial mitzvah to number the months of the year in accordance with the event of Yetzias Mitzrayim no longer applies. Instead of the initial mitzvah (which applied from the time of our coming forth from Egypt until the time of the redemption from Babylon,) the mitzvah is now to call the months by their Persian names, as Ramban writes in his above-mentioned commentary to the Torah. ((See Beis Shlomo, no. 22, who writes that although the names are Persian in origin, they should not be looked down on, because they were instated by the Anshei Keneses Hagedolah, and surely contain deep secrets.))

Rav Yitzchak Abarbanel, however, writes in his commentary to the Torah (and in Rosh Emunah, chap. 13) that the reason we are permitted to call the months by their Persian names is only because we also continue numbering them in accordance with Yetzias Mitzrayim. As he writes: “Yet, the names of the months that we use, which were brought with those who ascended from Babylon were not a transgression the mitzvah, because even they continued to number the months as ‘the first month’, ‘the second month’, and so on, in accordance with instruction of the Torah. Aside from the number, they also referred to the month by the name that was used in Babylon.”

This approach is supported by one of the homilies (derashos) given by Ramban. He writes (homily for Rosh Hashanah), “we do not mean to change the names of the months, and forget our redemption from Egypt, but rather to append the Babylonian names, to declare and recall that we were exiled to Babylon, and Hashem delivered us .”

A similar yet distinct approach is mentioned by Maharam Chaviv (Ein Yaakov, beginning of Megillah). In his opinion, the mitzvah was not to call the month by its number, and it is therefore permitted to call the months of the year by any name we wish. The mitzvah, rather, is that whenever we number (as opposed to name) the month, we should recall the redemption from Egypt by establishing the first month as the month on which we were redeemed.

Mentioning the Number of the Month in Gittin and Documents

Beis Shlomo (no. 22) sides with  Abarbanel, whereby the mitzvah of numbering the month by the event of Yetzias Mitzrayim applies even today. Based on this premise, Beis Shlomo questions why we do not find any enactment of this ruling in the writings of rishonim and acharonim. Even in the halachic writings of Ramban himself, it is not mentioned. If this is the principle halachah, why is it not upheld at least in gittin and other legal documents?

In response to this question, Beis Shlomo quotes two possible answers. One is that the custom, at the time of the Talmud, was to write the date according to the ‘calendar of kings.’ Because the year of a king begins in the month of Tishrei, and not in the month of Nissan, it was impossible to use the number of the month as counted from Nissan. A second answer is that for gittin we specifically use the date from the creation of the world. Because halachah follows the opinion that the world was created in Tishrei, it follows that the months cannot be numbered from Nissan.

However, these answers do not explain why we make no mention of the number of the month in kiddush ha-chosesh recited on the Shabbos before Rosh Chodesh. To explain this difficulty, Beis Shlomo writes that it is possible that other authorities do not concur with the ruling of Ramban, and maintain that there is no mitzvah to label the months by their number from the month of Nissan. This, he notes, is the common custom.

Indeed, it should be noted that Rambam makes no mention (in Mishnah Torah and elsewhere) of the mitzvah to count the months. It likewise emerges from the commentaries of a number of rishonim (Rashba, Ritva, Ran to Rosh Hashanah 3a) that they do not share Ramban’s opinion on this matter.

The Hungarian Tradition of Jewish Dates

Although, as mentioned, most halachic authorities do not broadly uphold the obligation to use a particular system of months, the Hungarian tradition treats the matter with utmost stringency. According to Chasam Sofer (Toras Moshe, Parashas Bo), there is an obligation to begin one’s letters with the number of the day of the week (counting from Sunday), and the number of the month (counting from Nissan): “This is an explicit rebuke [to those who do not use the Jewish calendar]: We should write in our letters and similar documents the first day of the week, first month of the year, and so on, to testify that Hashem created the world in six days, ‘and He rested on the seventh,’ and to remember the redemption from Egypt—and not Heaven forbid, the date of the nations.”

Chasam Sofer reiterates his stance in his homilies (Homily for Seventh of Av, 570), in which he writes: “Those who want to reform, and begin their letters with the year of the birth of the Christian messiah, are writing and signing away their portion for the world to come!” According to Chasam Sofer, there is a prohibition in using secular dates, concerning the days of the week, the months of the year, and the year itself.

This principle is clearly illustrated in the writings of Maharam Schick (Yoreh De’ah, no. 171) the foremost disciple of Chasam Sofer. He explains that besides the prohibition of using non-Jewish months (as drawn from Ramban), using the secular count of years transgresses the prohibition of “You shall not mention the names of other gods,” because the count is based on the Christian idolatry. Based on this ruling, he writes that a tombstone on which the secular date is inscribed must be smashed.

Aside from the Hungarian tradition, it is interesting to note that Get Pashut, questions the validity of a get on which the secular date was written. ((Concerning the matter of a get, see Aruch Hashulchan (127:44), who writes that the get is valid in spite of its non-Jewish date, though he concludes by stating that the matter requires further investigation. Levush (127:11), however, writes that is it the custom to write only the Jewish date, and the use of a non-Jewish date casts serious doubt over the validity of the get.)) He continues that even in secular letters one should be wary of quoting the Christian calendar, and rather use the count of years from the creation of the world.

Other Opinions

Many modern day authorities take a more lenient stance than that of Chasam Sofer and his disciples.

One of the most interesting and comprehensive halachic discussions of the subject is found in Yabia Omer (vol. 3, Yoreh De’ah, no. 9). Rav Ovadyah Yosef challenges the very premise whereby the secular count of years dates back to the birth of the Christian ‘savior’. Citing numerous proofs from Talmudic and other writings, Rav Yosef demonstrates that Yeshu lived long before [and at the very least four years before] the beginning of the Gregorian calendar. Quoting from Otzar Yisrael (vol. 5, p. 277) he proves that their year-count dates back to the Roman Empire, and not to the birth of Yeshu.

He adds that even if we do assume that those who use the secular dating system implicitly refer to the common presumption that the year refers to the birth of Yeshu, there would still be no prohibition of “going in their ways,” because this prohibition applies only to cases in which we do not know the rationale behind the non-Jewish ways, or cases in which the custom involves immodesty (Beis Yosef, Yoreh De’ah 175). With regard to the dating system, these concerns do not arise.

He also notes that we find many Jewish leaders over the generations who used non-Jewish dates in their letters, such as Shach (who dates a letter February 3rd, 1660), Maharam Padwa, and others. Moreover, the publication details of Torah volumes always made reference to non-Jewish dates, and never was an objection heard.

Indeed, there is known to be a letter from the Chasam Sofer on which the non-Jewish date appears. The letter was addressed to the secular government, and it was, of course, appropriate and necessary to use the secular date, yet we nonetheless see that the prohibition is not absolute. Regarding the strong wording of Chasam Sofer, Rav Ovadyah explains that he was referring specifically to those who were seeking to “reform” the traditional Jewish ways, and his strongly worded response was intended for them alone.

Finally, Rav Ovadyah concludes: “It is therefore clear that there is no prohibition whatsoever in using the secular date. Nonetheless, there remains a virtue [of using the Jewish date], and whenever there is no great need, the months and years should be written according to the dating of Israel—and particularly in our holy land. When there is a need to write the secular date, it is good to also make mention of the count of years from Creation.”

A very similar position to Yabia Omer is taken by Tzitz Eliezer (vol. 8, no. 8). Yet, the two disagree over the preferable way in which non-Jewish months should be written. According to Yabia Omer, it is preferable to write out the name of the secular month in full (January, February, and so on), and not to mention the number of the month, so as not to uproot the number of the month counting from Nissan. Tzitz Eliezer, however, writes that it is better to use the number of the month, and not to mention its name, because one should make no mention of the non-Jewish months, whose names derive from idolatry.

Although he opines that no prohibition is involved, Tzitz Eliezer writes that one who uses the non-Jewish count of years should append the word leminyanam or lemisparam (according to their count). If the Jewish count is also mentioned, he writes that the practice of mentioning both dates is unquestionably permitted. ((See also Rav Moshe Sternbuch (Teshuvos Vehanhagos vol. 1, no. 830), who writes that there is no question of a transgression in using non-Jewish dates, though he also adds that it is preferable to number the Torah months, and fulfill a mitzvah (based on Ramban).))


  • According to Ramban, there is a mitzvah to count the months from Nissan, the month on which we were redeemed from Egypt. Most commentaries maintain that this mitzvah would still apply today, though some maintain that there is no problem in using names for months, and the mitzvah only applies when one wishes to actually number the month of the year. It would seem that many authorities do not concur with Ramban, and maintain that there is no mitzvah of counting the months from Nissan.
  • Authorities concur that it is preferable to use the Jewish dates, rather than secular dates, in writing letters and other documents. Some write that one should try to number the month in question (from Nissan).
  • Most authorities write that there is no prohibition in using secular dates. The Hungarian tradition, however, sees the matter in a more stringent light.
  • When using non-Jewish dates, most authorities maintain that one should write out the name of the month in full, rather than write a number. Some (Be’er Moshe) also write that one should seek to write the year in short rather than in full (10 rather than 2010).

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