Sapphos works on a 3:1 system. This means three in-character years (called Turns) will pass for each real-world, out of character year (called years). In an ideal world, that would mean one IC month passes roughly every ten days. However, months surrounding major site-wide events will usually be given a longer time. Months when nothing is slated to happen site-wide will often be shortened.
For this reason, back dating and fore dating of threads is encouraged.
ALL THREADS should have a date. This is not currently a mandatory rule, but it is preferred.
Sapphos works on a Turn-based dating system, rather than an Interval/Pass based dating system as you might have seen on other sites.
We are in the Fifth Pass. However, dates are written based on the current Turn (1245 at the time of this writing)
Dates are written, with some personalizations, as Month/Day/Turn. Thus, 1/26/1245 takes place at the end of Month 1, on day 26, Turn 1245.
There are 13 months per Turn on Pern. There are 28 days per month. There are 50 Turns per pass, and 200 Turns per interval. Passes are numbered before Intervals. Thus, Pass One is followed by Interval One, which is then followed by Pass Two. In the event that you need a suffix, perhaps for emphasis, the dating system is 'A.L.' The meaning of this is 'after Landing,' however, the actual meaning of that phrase has been lost to history.
This is the current schedule for month-changes on Sapphos