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
Mesoamerican Long Count calendar the GMT correlation is historical, astronomical and archaeological: Historical: Calendar Round dates with a corresponding Julian date are recorded in Diego de Landa's "Relación de las cosas de Yucatán" (written circa 1566), the Chronicle of Oxcutzkab and the books of Chilam Balam. De Landa records a date that is a Tun ending in the Short Count. Oxkutzcab contains 12 Tun endings. Bricker and Bricker find that only the GMT correlation in consistent with these dates. The Book of Chilam Balam of Chumayel contains the only colonial reference to classic long-count dates. The Julian calendar date of 11.16.0.0.0 confirms the GMT