Details about today's date with count of days, weeks, and months, Sun and Moon cycles, Zodiac signs and holidays. Find out today's date, current time, day of the week, week number, and more. Your complete date and time resource. The time taken for the Earth to make a full rotation about its axis with respect to the fixed stars; a sidereal day or stellar day. (informal or meteorology) A 24-hour period beginning at 6am or sunrise. On average, this is 24 hours (86,400 seconds). As a day passes at a given location it experiences morning, afternoon, evening, and night. This daily cycle drives circadian rhythms in many organisms, which are vital to many life processes. The meaning of DAY is the time of light between one night and the next. How to use day in a sentence. Find out what happened today or any day in history with On This Day. Historical events, birthdays, deaths, photos and famous people, from 4000 BC to today. DAY definition: 1. a period of 24 hours, especially from twelve o'clock one night to twelve o'clock the next night…. Learn more. A day is a 24-hour period, or the length of time it takes the Earth to rotate fully on its axis. There are 365 days in a year, and 31 days in the month of January. DAY meaning: 1. a period of 24 hours, especially from twelve o'clock one night to twelve o'clock the next night…. Learn more. Daytime length or daytime duration is the time elapsed between beginning and end of the daytime period. Given that Earth's own axis of rotation is tilted 23.44° to the line perpendicular to its orbital plane, called the ecliptic, the length of daytime varies with the seasons on the planet's surface, depending on the observer's latitude. [5].