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,
Tenpō calendar new moon. A leap month is added when there are three lunar months between a lunar month which includes a solstice/equinox and the following lunar month which includes a solstice/equinox. In that case the leap month is the lunar month which does not include any (one of the twelve solar terms that are used to determine the months of the year). The months which include a solstice/equinox are fixed as the second, fifth, eighth and eleventh months respectively. The time of the day used in the calendar to determine the dates of solar terms and lunar phases is that observed