This library is optimization of https://github.com/udivankin/sunrise-sunset for repeated large scale sunrise/sunset calculations for multiple location.
This library is probably NOT the library you're looking for. For one time or user driven sunrise/sunset calculation https://github.com/udivankin/sunrise-sunset has more user friendly interface.
For correct usage see src/__tests__
N.B. Some important bugs inherited from original lib where fixed. See udivankin#19 (comment)
N.B. This library results deviate with up to two minutes from more complicated calculations from https://www.suncalc.org/ and alike, but I find the results useful given how stretchy definition of sunrise/sunset can be.