<P> The Jewish calendar is based on the Metonic cycle of 19 years, of which 12 are common (non-leap) years of 12 months and 7 are leap years of 13 months . To determine whether a Jewish year is a leap year, one must find its position in the 19 - year Metonic cycle . This position is calculated by dividing the Jewish year number by 19 and finding the remainder . For example, the Jewish year 5778 divided by 19 results in a remainder of 2, indicating that it is year 2 of the Metonic cycle . Since there is no year 0, a remainder of 0 indicates that the year is year 19 of the cycle . </P> <P> Years 3, 6, 8, 11, 14, 17, and 19 of the Metonic cycle are leap years . To assist in remembering this sequence, some people use the mnemonic Hebrew word GUCHADZaT "גוחאדז" ט "‬, where the Hebrew letters gimel - vav - het aleph - dalet - zayin - tet are used as Hebrew numerals equivalent to 3, 6, 8, 1, 4, 7, 9 . The keviyah records whether the year is leap or common: פ for peshuta (פשוטה), meaning simple and indicating a common year, and מ indicating a leap year (me'uberet, מעוברת). </P> <P> Another memory aid notes that intervals of the major scale follow the same pattern as do Jewish leap years, with do corresponding to year 19 (or 0): a whole step in the scale corresponds to two common years between consecutive leap years, and a half step to one common year between two leap years . This connection with the major scale is more plain in the context of 19 equal temperament: counting the tonic as 0, the notes of the major scale in 19 equal temperament are numbers 0 (or 19), 3, 6, 8, 11, 14, 17, the same numbers as the leap years in the Hebrew calendar . </P> <P> A simple rule for determining whether a year is a leap year has been given above . However, there is another rule which not only tells whether the year is leap but also gives the fraction of a month by which the calendar is behind the seasons, useful for agricultural purposes . To determine whether year n of the calendar is a leap year, find the remainder on dividing ((7 × n) + 1) by 19 . If the remainder is 6 or less it is a leap year; if it is 7 or more it is not . For example, the remainder on dividing ((7 × 5778) + 1) by 19 is 15, so the year 5778 is not a leap year . The remainder on dividing ((7 × 5779) + 1) by 19 is 3, so the year 5779 is a leap year . This works because as there are seven leap years in nineteen years the difference between the solar and lunar years increases by 7 / 19 - month per year . When the difference goes above 18 / 19 - month this signifies a leap year, and the difference is reduced by one month . </P>

What is the sixth month in the jewish calendar