Its not excactly 19 years because of Secular Leap Days.
Also the Jewish Calender is slightly off.
The Earth Revolved around the Sun in 365 Days 5 Hours 49 Mins
The Jewish Calender assumes the Rotation is 365 Days 5 Hours 55 Mins.
Which adds about 5 Mins to every year , Over 1700 years its about a week off