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Hi, thanks for using Hebcal.
Candle-lighting and Havdalah times are derived from sunset times, which are approximated from a location (latitude, longitude) and day of year. As of August 2020, Hebcal.com calculates zmanim (halachic times) using an algorithm published by the US National Oceanic and Atmospheric Administration. The NOAA solar calculator is based on equations from Astronomical Algorithms by Jean Meeus.
Since 2013, Hebcal.com has been using lat/long definitions from GeoNames.org, which is available under a Creative Commons license. For the USA, we purchase a commercial ZIP code database from zip-codes.com that provides latitude and longitude for the “center” of each zipcode.
For more details, see this page:
https://www.hebcal.com/home/94/how-accurate-are-candle-lighting-times
Customer support service by UserEcho
Hi, thanks for using Hebcal.
Candle-lighting and Havdalah times are derived from sunset times, which are approximated from a location (latitude, longitude) and day of year. As of August 2020, Hebcal.com calculates zmanim (halachic times) using an algorithm published by the US National Oceanic and Atmospheric Administration. The NOAA solar calculator is based on equations from Astronomical Algorithms by Jean Meeus.
Since 2013, Hebcal.com has been using lat/long definitions from GeoNames.org, which is available under a Creative Commons license. For the USA, we purchase a commercial ZIP code database from zip-codes.com that provides latitude and longitude for the “center” of each zipcode.
For more details, see this page:
https://www.hebcal.com/home/94/how-accurate-are-candle-lighting-times