![]() Depending on the time of year and the latitude of the observer, twilight can expire in less than an hour or linger throughout the night! Twilight is always shortest in the tropics, where less than one hour is the most you ever get. Twilight’s duration is not usually expressed in units of time, but rather degrees, and for good reason: its length varies. Stages of dawn occur before sunrise, in the reverse order as described for dusk. (Sunset can be defined as the moment when the top of the sun’s disk has passed the horizon.) As with twilight, there is civil dusk, nautical dusk, and astronomical dusk, occurring at the exact moment when the center of the sun’s disk is at 6°, 12°, and 18° below the horizon, respectively. See the Almanac’s sunrise/set calculator to get all three twilight times!īy the way, twilight is different than dusk, which occurs after sunset. The conclusion of this stage of twilight heralds the arrival of full darkness. After this point, the faintest stars emerge. Astronomical twilight occurs when the sun’s center is between 12 and 18 degrees below the horizon.After this, the horizon vanishes, when a mariner cannot distinguish between sea and sky. Nautical twilight occurs when the sun’s center is between 6 and 12 degrees below the horizon.That’s when streetlights must be on, according to most municipal ordinances. Civil twilight starts at sunset and ends roughly 45 minutes later, when the sun’s center has plunged six degrees below the horizon-equal to 12 times its own width.These stages also occur before sunrise, in the reverse order. Below describe the stages of twilight as they occur in the evening. And there’s really not one twilight but three! And they’re each so distinct, they have their own names. ![]() But in actuality, it’s a very specific event. What is the correct definition of twilight? The concept suggest vagueness. The definitions are from the National Weather Service and more detail can be found in their glossary.Image: Earth at twilight. Blue sunlight fades into darkness. Twilight refers to the period between the dawn and sunrise and between sunset and dusk. Sunset is the time when the last part of the Sun disappears below the horizon in the evening at a given location. Sunrise is the time when the first part of the Sun becomes visible in the morning at a given location. Respectively, dusk occurs when the Sun is 6° below the horizon in the evening. What are the definitions of dawn, dusk and twilight?ĭawn is the time of morning when the Sun is 6° below the horizon. Sunrise/sunset tables can be dynamically generated at these links: When do sunrise and sunset occur throughout the year? Another option would be to use 24-hour clock, using the designation of 0000 to refer to midnight at the beginning of a given day (or date) and 2400 to designate the end of a given day (or date). ![]() is a good idea, especially legal documents such as contracts and insurance policies. To avoid ambiguity, specification of an event as occurring on a particular day at 11:59 p.m. However, if a date/time is referred to as "at midnight on Friday, October 20th" the intention could be either midnight the beginning of the day or midnight at the end of the day. When someone refers to "midnight tonight" or "midnight last night" the reference of time is obvious. Is midnight the end of a day or the beginning of a day? Hours of operation for a business or other references to a block of time should also follow this designation rule.įor example, a business might be open on Saturdays from 8 a.m. The same is true for midnight, but there is an added issue of which day midnight refers to (see below). as soon as it the 12:00 appears, and not delay the display of the p.m. ![]() For example, it would be applicable for a digital clock changing from 11:59:59 a.m. It is fair to say, however, that the shortest measurable duration after noon should be designated as p.m. Also, midnight is both twelve hours before noon and twelve hours after noon. Since noon is neither before noon nor after noon, a designation of either a.m. To illustrate this, consider that "a.m." and "p.m." are abbreviations for "ante meridiem" and "post meridiem," which mean "before noon" and "after noon," respectively. This is a tricky question because 12 a.m. What are the definitions of dawn, dusk and twilight?Īre noon and midnight referred to as 12 a.m.When do sunrise and sunset occur throughout the year?.Is midnight the end of a day or the beginning of a day?.Are noon and midnight referred to as 12 a.m.Sunrise/sunset times and definitions of dusk/dawn/twilight.
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