Mesoamerican Long Count calendar the use of zero as a place-holder and presents one of the earliest uses of the zero concept in history. On Maya monuments, the Long Count syntax is more complex. The date sequence is given once, at the beginning of the inscription and opens with the so-called ISIG (Introductory Series Initial Glyph) which reads "tzik-a(h) hab’ [patron of Haab' month]" ("revered was the year-count with the patron [of the month]"). Next come the 5 digits of the Long Count, followed by the Calendar Round (tzolk'in and Haab') and supplementary series. The supplementary series is optional and contains lunar data, for
Year of three popes popes have held office in a given calendar year. Years in which the Roman Catholic Church was led by three different popes include: There was also a year in which the Roman Catholic Church was led by four popes, called the Year of Four Popes: Year of three popes A year of three popes is a common reference to a year when the College of Cardinals of the Catholic Church are required to elect two new popes within the same calendar year. Such a year generally occurs when a newly elected pope dies or resigns very early into his papacy.