As the question indicates, I would like to know the sunrise and sunset times of a location. This is to evaluate the impact of day and night variations of a time series. Is there a way to download this data? Is there some other way to divide the aforementioned time series into day and night for this purpose. I am new to this and any help would be greatly appreciated. It would be fine even if this is a paid service. Thanks.
You might want to find an astronomical almanach or year book. They usually have tables of sunrise and sunset times. They usually cover only one year, though and accurate times only for selected places.
You might also consult a tool of your choice like stellarium or use websites like Heavens Above to check the sunset and sunrise times for specific locations. This allows you often arbitrary choice of a location and a large range in time.
Either case, make sure you use a reference with a location near you or get your geographic coordinates as accurate as you can... 100km already make several minutes of difference. If you need an accuracy of only to about one or two minutes: then you can get the data from one year and re-use it for any other.
Generally: the rise and set times of the sun do repeat roughly yearly, but not exactly: we do have leap years which account for the fact one revolution of Earth around the Sun does not fit an exact integer number of days in a year. But one can calculate this to reasonably great precision as the equation of motions and the current positions and speed and masses of all important objects in the Solar System are reasonably-well known. And thus one can predict the future or get knowledge about it in the past up to a certain extend (this extend can well be many millenia, depending on required accuracy and property.