<Tr> <Th> 2018 </Th> <Td> 20 </Td> <Td> 16: 15 </Td> <Td> 21 </Td> <Td> 10: 07 </Td> <Td> 23 </Td> <Td> 01: 54 </Td> <Td> 21 </Td> <Td> 22: 23 </Td> </Tr> <Tr> <Th> 2019 </Th> <Td> 20 </Td> <Td> 21: 58 </Td> <Td> 21 </Td> <Td> 15: 54 </Td> <Td> 23 </Td> <Td> 07: 50 </Td> <Td> 22 </Td> <Td> 04: 19 </Td> </Tr> <Tr> <Th> 2020 </Th> <Td> 20 </Td> <Td> 03: 50 </Td> <Td> 20 </Td> <Td> 21: 44 </Td> <Td> 22 </Td> <Td> 13: 31 </Td> <Td> 21 </Td> <Td> 10: 02 </Td> </Tr> <P> Astronomical timing as the basis for designating the temperate seasons dates back at least to the Julian calendar used by the ancient Romans . It continues to be used on many modern Gregorian calendars worldwide, although some countries like Australia, New Zealand, and Russia prefer to use meteorological reckoning . The precise timing of the seasons is determined by the exact times of transit of the sun over the tropics of Cancer and Capricorn for the solstices and the times of the sun's transit over the equator for the equinoxes, or a traditional date close to these times . </P>

What is the four seasons of the earth