THE NOJOKAN CALENDAR
The Vulcan calendar was referenced in "Yesteryear" (TAS3) by D. C. Fontana, the system in use worldwide on Vulcan since the Reformation when the tosri [Velprâla r'tas] was defined at exactly 12 rirorks [t'ved], 252 sunrise-to-sunrise rorirks [v'hral]. It seems to have been first used, based on its zero point, Jan. 18, 752 BC. 8877/12/20 AV (Anno Vulcanis) is equated with the Earth date 2237/12/07 AD, the date of Spock's life being saved by Sele, in several sources. In Alan Dean Foster's adaptation based upon Capt. James Kirk's log (Galactic Historial Archives on S. Monicus I) however the Earth and Vulcan years are confused and the stardate is misprinted as 5373.4 rather than 6373.4 (Dec. 2273). The 50 "years" of Sarek's time on Earth before meeting Amanda Greyson are actually tosri.
It is this dating system that is used in certain Tech Fandom books notably the Star Fleet Medical Reference. Gene Roddenberry's Star Trek: The Motion Picture supports this in a footnote which states that 9 Vulcan years (tosri) is approximately 2.8 Earth years.
According to the U.S.S. Enterprise Officer's Manual, which originally appeared in Geoffrey Mandel's Star Fleet Handbook, a Vulcan year (tosri) is equal to 123.02 Earth days. In Spock's World by Diane Duane) it is estimated that the Old Style Vulcan calendar was established approximately 943 tosri after the catastrophe caused by the solar flare.
According to T'Chai and Prof. Astrid Ferszt in The Mathematical History of the Vulcan Year by Sterk, T'san & Paul Andrejevitch (Universal University Books, Oxford, 2201) Vulcan is 52,360,000 miles or 0.5633 AU from its sun, 40 (omicron) Eridani, a F2 star 105 light-years from Sol. The three values above correspond reasonably well as seen in the following table of with the Officer's Manual being the most accurate.
tori rirork rorirk ritark rurerk unhro
ST:TMP 0.31y 0.026y 0.45d 0.60h 0.67m 0.74s
Officer's Manual 0.33681y 0.028068y 0.48817d 0.65089h 0.72322m 0.80357s
0.5633 AU from F2 0.3515y 0.029y 0.51d 0.68h 0.75m 0.84
time units: tosri ["one-year"] = 12 rirork ["twelfth-year"]
rirork = 21 rorirk ["twenty-first-(month)"]
rorirk = 18 ritark ["eighteenth-(day)"]
ritark = 54 rurerk ['fifty-fourth-(hour)"]
rurerk = 54 unhro ["(fifty-fourth)-squared-(hour)"]
month nicknames: 1 Snir [(to)snir(irork), "not twelth-year"]
2 Stirk [(to)stirk, "sixth-year"]
3 Srerk [(to)srerk, "quarter-year"]
4 Srark [(to)srark, "third-year"]
5 Nhrur [(tosn)nhrur(irork), "five-twelfth-year"]
6 Srork [(to)srork, "half-year"]
7 Stor [(to)stor(irork), "seven-twelfth-year"]
8 Nhror [(tosn)nhror(erk), "two-third-year"]
9 Nhrar [(tosn)nhrar(erk), "three-quarter-year"]
10 Nhrut [tosn)nhrut(irk), "five-sixth-year"]
11 Njan [njan(itosri), "not-one-year"]
12 Mit [mit(osri), "almost-one-year"]
NOTE: The twelfth month is given in "Yesteryear" as Tasmeen and in Vulcan's Heart as Shavreen.
The following table shows the Earth dates for AD 2002 corresponding to the current Vulcan tosri, 8179.