How can one calculate Jewish sunrise and sunset? I'm not necessarily asking for a formula. Just wondering if there's a difference between Halachik rise/set and what the world considers [e.g. science] rise/set, and if there is, what the difference is?
Although there is some discussion in the poskim about these questions, for practical purposes, one should use the regular times for sunrise and sunset listed for your locale. These times can be found in local newspapers or on the internet. It is best to adjust these times approximately two minutes, because astronomical conditions and slight variations in longitude between your exact location and the sites at which the sunrise/sunset calculations are made. A good website for these calculations is kashrut.com/zemanim.