One of the less-understood curiosities of Persian historiography in the Safavid period is the decision of several chroniclers to organize their work based on an Iranian adaptation of the Chinese-Uighur zodiac system—in which each year starts with the March equinox (Nawruz) and corresponds to an animal sign, in a repeating twelve-year cycle—rather than making exclusive use of the lunar Islamic calendar, or avoiding the annalistic format altogether, as had often been done in preceding centuries. The adoption of the animal-cycle convention in Safavid texts, as part of a hybrid dating system, raises several questions. How, and when exactly, did this practice originate? Was it related to fiscal or military record-keeping? What purposes did solar animal years serve for court historians? Beyond these questions, the use of multiple calendars has led to confusion in the chronology of certain events—including the accession of Shah 'Abbas I, which took place in 995/1587 but is often dated to 996/1588. A few modern scholars, notably Charles Melville and Robert D. McChesney, have offered general commentary on these difficulties or investigated specific cases. This paper takes a different approach to the issue of the "Iranian zodiac system" in Safavid chronicles, by reviewing several works that make use of animal years and evaluating the ways in which they attempt, with widely varying degrees of success, to maintain concordance with the Islamic calendar. Particular attention is paid to the Takmilat al-akhbar (978/1570) of 'Abdi Beg Shirazi and the Khulasat al-tavarikh (999/1591) of Qazi Ahmad Qumi. We arrive at a few potential insights, including that it was advantageous for historians of the early Safavid period to set their annals on a calendar that tracked the seasons, since the military and the court were semi-itinerant, moving between summer and winter pastures (yaylaq and qishlaq, respectively). There may also be something deliberately Persianizing in adopting a format in which the year begins with Nawruz. Finally, the very fact that chroniclers felt compelled to use this system, despite the obvious, acknowledged technical challenges that it posed, may be viewed as evidence of its basis in society.