Months:
In a leap-year, esfand is given a 30th day. This leap-day occurs when the Vernal Equinox (the sun appears to pass the equator from the southern to northern hemisphere) in Tehran time is after midday, thus making the next day 1 farvardin. This results in 8 leap years in roughly a 33 year cycle, currently falling on years 1, 5, 9, 13, 17, 22, 26, and 30, but this system must occasionally be pushed back one step.
The Jalaali also uses a 7 day week with Persian names for the days.
Days:
Links: