The traditional East Asian calendars divide a year into 24 solar terms . Xiàzhì or Geshi is the 10th solar term, and marks the summer solstice. It begins when the Sun reaches the celestial longitude of 90° and ends when it reaches the longitude of 105°. It more often refers in particular to the day when the Sun is exactly at the celestial longitude of 90°. In the Gregorian calendar, it usually begins around June 21 and ends around July 7.
The solstices mark the ''middle'' of the seasons in East Asian calendars. Here, the Chinese character means "extreme", so the term for the summer solstice directly signifies the summit of summer, a linkage absent in Western languages.