Winter solstice instant of the solstice can be calculated, direct observation of the solstice by amateurs is impossible because the sun moves too slowly or appears to stand still (the meaning of "solstice"). However, by use of astronomical data tracking, the precise timing of its occurrence is now public knowledge. One cannot directly detect the precise instant of the solstice (by definition, one cannot observe that an object has stopped moving until one later observes that it has not moved further from the preceding spot, or that it has moved in the opposite direction). Further, to be precise to a single 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: