Spring Equinox.[Photo/IC] The traditional Chinese lunar calendar divides a year into 24 solar terms. The Spring Equinox (Chinese: 春分), as the fourth term of the year starts on March 20 and ends on April 3 this year. The Spring Equinox signals the equal length of the day and night time. On the day of the Spring Equinox, sun is directly above the equator. After the equinox, the sun moves northwards, resulting in gradually longer day time in the Northern Hemisphere and longer night in the Southern Hemisphere. Here are things you may not know about the Spring Equinox. Swallows fly north The ancient Chinese people divided the fifteen days of the Spring Equinox into three "hou's," or five-day parts. As the old saying goes, swallows fly back to the North in the first hou; thunder cracks the sky in the second hou; lightning occurs frequently in the third hou, which vividly reveals the climate feature during the Spring Equinox.