For people in the Northern Hemisphere who huddled against a sometimes brutal winter, hope is here. Spring equinox 2021 arrives on Saturday, March 20, bringing its nearly perfect balance of daytime and nighttime all around the world.For people in the Northern Hemisphere who huddled against a sometimes brutal winter, hope is here. Spring equinox 2021 arrives on Saturday, March 20, bringing its nearly perfect balance of daytime and nighttime all around the world.