<Table> <Tr> <Td> </Td> <Td> This section does not cite any sources . Please help improve this section by adding citations to reliable sources . Unsourced material may be challenged and removed . (September 2017) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This section does not cite any sources . Please help improve this section by adding citations to reliable sources . Unsourced material may be challenged and removed . (September 2017) (Learn how and when to remove this template message) </Td> </Tr> <P> The March equinox occurs about when the Sun appears to cross the celestial equator northward . In the Northern Hemisphere, the term vernal point is used for the time of this occurrence and for the direction in space where the Sun is seen at that time, which is the origin of some celestial coordinate systems: </P> <Ul> <Li> in the ecliptic coordinate system, the vernal point is the origin of the ecliptic longitude; </Li> <Li> in the equatorial coordinate system, the vernal point is the origin of the right ascension . </Li> </Ul>

When would you have 24 hours of darkness in the southern hemisphere