Brian B.'s Climate Blog: Daylight-Twilight-Astronomical Maps
Sunrise and Sunset calendar. Sunrise, Sunset, Twilight, and Daylight Hours any city in the world
About Daylight Hours, Twilight, Civil Twilight, Nautical Twilight and Astronomical Twilight
Civil Twilight for Watch on the App Store
Skyclock Latest Version v1.5-4-gbbc2b37 for Android
What is astronomical twilight? | Space
trigonometry - How to calculate civil twilight timings? - Mathematics Stack Exchange
About Daylight Hours, Twilight, Civil Twilight, Nautical Twilight and Astronomical Twilight
Civil Twilight Calculator | App Price Drops
Sun rise, set and twilight times calculated using a simple iterative scheme and implemented as a QBASIC program, an Excel spreadsheet using VBA and as a plain spreadsheet.