Turning Clockwise: Jews and Timekeeping from Antiquity to Modernity | Dissertation Spotlight

David Zvi Kalman, “Unequal Hours: The Jewish Reception of Timekeeping Technology from the Bible to the Twentieth Century” (PhD diss., University of Pennsylvania, 2019).

This dissertation is a proof of concept for how Jewish history and the history of technology—fields which have traditionally interacted very little—can benefit from talking to one another.

Jewish historians have made some forays into the study of technology in the past. Studies of late antique rabbinic realia, such as the work of Leopold Löw (d. 1944), Samuel Krauss (d. 1948) and, more recently, Daniel Sperber, remain very important for understanding the rabbinic lexicon. Such studies, unfortunately, are not focused primarily on technological development; those that are, such as research into the Jewish reception of the printing press, are relatively few and focus on those exceptional technologies which were adopted relatively quickly and in full view of Jewish thinkers.

Most technologies do not fit this mold; prior to the Industrial Revolution, technologies tended to change slowly and incrementally. These changes often went unnoticed in the moment and were quickly forgotten after the fact; Jews, like others, spent little time writing about technological development or specific technologies prior to the early modern period. Because of these factors, along with the traditional way in Jewish historians specialize—in rabbinic literature, in the medieval literature, in early modern literature, etc.—most will not naturally inquire about Jewish technological engagement on the basis of the texts in their subfield. The interesting texts are just too few and too sparsely distributed. The investigation needs to begin from outside of Jewish texts.

In order to show the promise of examining Jewish history in a technological frame, I chose to study timekeeping technology, whose long and complex development touches every era and region in which Jews have lived. My dissertation took the form of a single, extended narrative, one that begins with the Hebrew Bible and ends, somewhat arbitrarily, at the beginning of the twentieth century. In theory, the study should have ended in the twenty-first century, but (forgive me) time pressures excluded that possibility. I hope to cover this material when turning this study into a book.

Evidence for the twelve-part division of the night (the day probably came a little later) exists in Egypt from at least 2150 BCE. The first timekeeping technologies—the sundial and clepsydra (water clock)—appear as early as 1500 BCE. For its part, the Hebrew Bible shows little interest in timekeeping. The sole references to “hours” appear in the Aramaic section of the Book of Daniel (see Daniel 3:6, 4:16, and 4:30); here they are not used in a technical sense, but simply mean “a short amount of time.” This is, in fact, the original meaning of the term, not only in Aramaic but also in Greek; in the latter, it was only in the fourth century BCE that the term gained a technical meaning. While the Bible may contain a reference to a sundial in the story of the “Dial of Aḥaz” (see Is. 38:4–8 and 2 Kings 20:9–11), it is in keeping with contemporaneous usage that the device is in a palace, out of the public’s reach.

The earliest definitive evidence for Jews adopting a formal timekeeping system appears in the apocryphal Astronomical Book, a version of which appears in 1 Enoch 72–82. Both the Ethiopic and fragmentary Aramaic versions of this book divide the day into parts (but not hours); in particular, the fragmentary Aramaic version of this book appears to divide the night into fourteen parts. Jonathan Ben-Dov has suggested that Jews modified an existing Babylonian fifteen-part day because of the prior significance of the number seven Jewish culture (see Ben-Dov, Jonathan, Head of All Years (Brill, 2008), 77). Whatever its prevalence, this system was permanently drowned out by the Greco-Roman use of the twelve-hour day; apart from a possible use of the hour in a reconstructed Qumran fragment, the first definitive use of the twelve-hour day is in the writings of Greek-speaking Jews.

Though Jews quickly and fully embraced the twelve-hour day, I argue that the rabbinic use of the system has been misunderstood. Over the past hundred years, people living in rich countries have become accustomed to new technologies quickly being adopted by a large portion of the population; as a result, one might theorize that sundials and clepsydras and the twelve-hour system they employed caused Jews, Romans, and others to keep track of time more carefully. In reality, this does not appear to have been the case; yes, timekeeping devices did proliferate—there are several in ancient synagogues—but they were often purely ornamental, with serious use confined to special situations, like astronomy and the court system (where speeches were timed). Thus, while the rhetoric of the twelve-hour day was widely adopted, late antique rabbis did not take full advantage of it; instead, they just expressed their low-precision expectations in high-precision language.

One of the more fascinating ways in which this can be seen is in a statistical analysis of the various hours of the day as they appear in late antique rabbinic literature. While sundials theoretically made it just as easy to coordinate events for any of the day’s twelve hours, in reality the rabbis heaped considerable attention on just four of those hours: the third/fourth, sixth, and ninth. Other hours are mentioned much less frequently, sometimes only in the context of a narrative describing how God created Adam over the course of twelve hours on the sixth day (see bSanhedrin38b and elsewhere). This usage pattern, I argue, suggests that the rabbis, despite adopting the Greco-Roman system wholeheartedly, really only expected the public to divide the day into quarters; indeed, in bAvodahZarah3b they imagine God’s daily itinerary as being divided up in precisely this manner. There is evidence that the Romans used a four-part division of the day, as well.

Rabbinic usage of the hour system is less precise that it first appears in another way. While Maimonides would later declare that rabbinic “hours” were always seasonal hours (shaʿot zemaniyyot)—that is, hours which are always 1/12 of the length of a given day (or night)—there is in fact no evidence that the rabbis understood the concept of the seasonal hour, nor is there evidence that they understood its alternative, the equinoctial hour, which is always 1/24 of a day/night cycle. Instead, I argue that the rabbinic understanding of the hour was essentially naïve: they assumed that hours always remained the same length, but also assumed that there were always twelve hours in a day (or night). These two assumptions cannot both be true, but that is the point: this incoherence actually explains why rabbinic usage of the word “hour” seems to shift from one meaning to the other, sometimes within a single text, and why the rabbis never bother clarifying how they are using the term.

The fuzziness of the rabbinic conceptualization of the hour was enabled not just by loose timekeeping expectations, but by an accident of geography. As the map below indicates, all the centers of late antique rabbinic learning were located at or below the 34th parallel north; at these latitudes, the day does not fluctuate all that much over the course of the year. These relatively small fluctuations, combined with the rabbis’ low expectations about the public’s timekeeping abilities, meant that the rabbis could get away with not knowing or not caring about these two distinct valences of the term “hour.”

A map of major centers of Jewish scholarship in Late Antiquity and the medieval period. The difference in time between the longest and shortest day of the year at various latitudes is indicated.

Though the rabbis of Late Antiquity firmly and permanently cemented Greco-Roman timekeeping terminology in Jewish law, this legacy was received somewhat differently by Jews in Islamic and Christian lands. In the former, Jews scholars imbibed a great deal of theoretical timekeeping knowledge; it is here that Jews writing in Judaeo-Arabic began referring to seasonal hours (sāʿāt zamāniyyah), a term which Maimonides acknowledged was borrowed from astronomers (munajjimūn). A strong understanding of timekeeping is evident in the calendrical writings of Abraham bar Ḥiyya, Moses Maimonides, and Abraham ibn Ezra, the last of whom also wrote several works on the construction of astrolabes. At the same time, this understanding did not correspond with an increase in the public’s timekeeping abilities; as a result, this theoretical knowledge generally did not result in greater normative expectations. For its part, Islamic law placed less emphasis on the twelve-hour day than the Romans; Karaite law, which developed under Islamic rule, eschewed hour-based timekeeping, as well.

The situation in Christian Europe could not have been more different. Though the use of the twelve-hour day in late antique Christian writings (including the New Testament itself) ensured its preservation within the church, theoretical timekeeping knowledge had not been well-preserved, and public sundials—often on churches—were crude compared to their Greek and Roman counterparts. It was only in monasteries that sophisticated water clocks were used, though even here it appears that they were not of great importance. Climate worked against these technologies, too: the skies of Europe, cloudier than those in the Middle East, made sundials less effective, and the many nights during the year when the temperature dipped below freezing meant that water clocks were not reliable, either.

While neither the church nor European rabbis grappled much with timekeeping on a theoretical level, their location at relatively northerly latitudes forced them to deal with it on a practical level. Monastery regulations dictated that more psalms be recited during winter nights than summer nights, but the increase did not correspond with the increase in the length of the night. For their part, rabbis in northern France and Germany were the first to grapple with how rabbinic regulations might need to be tweaked in winter or summer months. Most impressively, the tosafists appears to have independently arrived at the twin concepts of seasonal and equinoctial hours in an attempt to understand two Talmudic passages (bEruvin56a and bRoshHashanah25a).

It was into this Christian European timekeeping environment that the mechanical clock first emerged. The devices first appeared around 1300 CE (give or take a couple of decades) and started proliferating rapidly across Europe in public spaces beginning in the 1370s. Though the accuracy of the first clocks was dismal, their presence was immediately felt because they brought with them a new mechanism for ringing out the hours. Whereas previously the meaning of a ringing bell could vary between cities and needed to be gleaned from context (time of day, anticipated public events, etc.), the new mechanism always struck once for the first hour, twice for the second hour, and so on. This new system meant that the public could now reckon the time down to the hour with great ease.

Though Jews were not involved in the construction of the new clocks, they quickly reacted when tower clocks started ringing out in their towns; the earliest Jewish acknowledgments appear around 1400 CE, within a generation of the first major proliferation. Jewish reactions to the new technology played out differently in Italy and Ashkenaz; there was also a weaker response in the Ottoman Empire beginning in the sixteenth century after the Ottomans had begun importing the devices.

In Italy, acknowledgment of the mechanical clock appears frequently in the colophons of manuscripts; copyists began to indicate not only the date at which they finished a book, but also the hour, and book owners recorded the hours at which birth, deaths, and miraculous events took place. These colophons universally employ the “Italian hours,” a convention for using mechanical clocks in which the clock runs for a single 24-hour cycle beginning at sunset (so, for example, “22 hours” means two hours before sunset). Usage of this convention is so consistent that, I suggest, it can be used to determine the provenance of the author. (Italian hours were standard in Poland, as well).

In Ashkenaz, by contrast, rabbis began contemplating whether the ringing of the mechanical clock should be afforded legal significance. It was in these deliberations that the concept of “seasonal hours” first begins to appear regularly in Jewish texts; the term was most likely popularized in Hebrew following the 1492 Naples printing of Judah al-Ḥarīzī’s translation of Maimonides’ commentary on the Mishnah. While it is not clear whether the mechanical clock led to any immediate practical changes in the law, it forced rabbis to clarify regulations—or the gap between regulations and communal practice—in ways that had not previously been necessary.

In the seventeenth century, clocks and watches took a few important leaps forward in accuracy; in the early eighteenth century, the minute hand became a standard feature of clocks. With these advances in accuracy, new legal debates began to emerge. The legally-significant definition of how long it takes to walk a mil, for example, had ranged between 18 minutes (technically, 1/3 hour + 1/30 hour) to half an hour, but in practice most people would not have been able to distinguish the two; now that they could, it suddenly became important to justify the positions and determine which was to be followed. At the same time, increasing Christian toleration of Jews led to a change in how Jews employed clocks in the public square: from the eighteenth century, Jews began incorporating clocks into their portraiture and synagogue exteriors, although still in a limited fashion.

There is much more to tell about the Jewish relationship to timekeeping that I have not been able to cover here. Whether or not one is interested in timekeeping, I hope that this study encourages other Jewish historians, including those who specialize in antiquity, to consider incorporating the history of technology into future studies. There is much here to explore.

David Zvi Kalman is Fellow in Residence at the Shalom Hartman Institute of North America; he is also an affiliated scholar with the Herbert D. Katz Center for Advanced Judaic Studies at the University of Pennsylvania and the owner of Print-O-Craft Press.