day [d] Unit Converter

Definition of day [d] unit

A day is a unit of time equal to 24 hours, or 86,400 seconds, representing one complete rotation of Earth relative to the Sun. In everyday usage, it extends from midnight to midnight and is divided into daytime and nighttime.

History of day [d] unit

The day originated from humanity’s observation of the repeating cycle of sunrise and sunset caused by Earth’s rotation. Ancient civilizations measured it using shadows, sundials, and water clocks, while calendars gradually formalized its relationship with lunar and solar cycles. The 24-hour division developed in ancient Egypt, where daylight and nighttime were each traditionally divided into twelve parts. Babylonian mathematical traditions influenced later timekeeping. Modern science defines the day through the second, with the conventional 24-hour solar day serving civil life, while astronomy also distinguishes it from the shorter sidereal day.

Applications of day [d] unit

Days organize schedules, calendars, work shifts, travel plans, school timetables, and legal deadlines. A 24-hour day is used in civil timekeeping worldwide, with clocks displaying hours, minutes, and seconds. Scientists use days to report weather patterns, biological rhythms, and astronomical observations. In computing and finance, day-based intervals support date calculations, billing periods, interest accrual, and data analysis.

Complete list of day [d] unit conversion

• second [s] = 1.1574074074074E-5 day [d]
• millisecond [ms] = 1.1574074074074E-8 day [d]
• minute [min] = 0.00069444444444444 day [d]
• hour [h] = 0.041666666666667 day [d]
• week = 7 day [d]
• month = 30.4375 day [d]
• year [y] = 365.25 day [d]
• decade = 3652.5 day [d]
• century = 36525 day [d]
• millennium = 365250 day [d]
• microsecond [µs] = 1.1574074074074E-11 day [d]
• nanosecond [ns] = 1.1574074074074E-14 day [d]
• picosecond [ps] = 1.1574074074074E-17 day [d]
• femtosecond [fs] = 1.1574074074074E-20 day [d]
• attosecond [as] = 1.1574074074074E-23 day [d]
• shake = 1.1574074074074E-13 day [d]
• month (synodic) = 29.53058912037 day [d]
• year (Julian) = 365.25 day [d]
• year (leap) = 366 day [d]
• year (tropical) = 365.24219 day [d]
• year (sidereal) = 365.256363004 day [d]
• day (sidereal) = 0.99726956632908 day [d]
• hour (sidereal) = 0.041552898597045 day [d]
• minute (sidereal) = 0.00069254830995075 day [d]
• second (sidereal) = 1.1542471832513E-5 day [d]
• fortnight = 14 day [d]
• septennial = 2556.75 day [d]
• octennial = 2922 day [d]
• novennial = 3287.25 day [d]
• quindecennial = 5478.75 day [d]
• quinquennial = 1826.25 day [d]
• Planck time = 6.239869212963E-49 day [d]