Winter solstice one must be able to observe a change in azimuth or elevation less than or equal to about 1/60 of the angular diameter of the sun. Observing that it occurred within a two-day period is easier, requiring an observation precision of only about 1/16 of the angular diameter of the sun. Thus, many observations are of the day of the solstice rather than the instant. This is often done by observing the sunrise and sunset or using an astronomically aligned instrument that allows a ray of light to be cast on a certain point around that time. Length of day
Academic term Kippur. Winter zman starts after Sukkot and lasts until just before Passover, a duration of five months (six in a Jewish leap year). Summer semester starts after Passover and lasts until either the middle of the month of Tammuz or Tisha B'Av, a duration of about three months. During the interim periods, which are called "bein hazmanim" (between the terms), students are on vacation. In Italy, all schools start in the first half of September, even though the exact beginning date changes every year. For schools from primary schools to high schools, the academic year is split into two semesters: