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Convert seconds to days

Please provide values below to convert second [s] to day [d], or vice versa.



Definition: A second is the base unit of time in the International System of Units (SI). It is defined based on cesium frequency, ΔνC, "by taking the unperturbed ground-state hyperfine transition frequency of the caesium-133 atom to be 9,192,632,770 when expressed in hertz, which is equal to s-1." This definition was adopted in late 2018, and is largely the same as the previous definition, except that the conditions are more rigorously defined.

History/origin: Unlike many units that have had numerous definitions throughout history, the second has only had four different definitions.

The second was historically defined as 1/86400 of a day in 1832, which was based on the definition of a day as the approximate amount of time required for the Earth to complete a full rotation cycle relative to the sun.

The second was also defined as a fraction of an extrapolated year in the late 1940s with the advent of quartz crystal oscillator clocks. This resulted in a second defined as "1/31,556,925.9747 of the tropical year for 1900 January 0 at 12 hours ephemeris time," in 1956. This definition was adopted as part of SI in 1960.

In 1967, the second was defined exactly as "9,192,631,770 times the period of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom." This definition has since been updated as of late 2018 to be more rigorously defined, but otherwise, is effectively the same. This new rigor does not affect how the second is used in everyday life.

Current use: As the SI base unit of time, the second and its multiples are ubiquitous. There are few, if any, modern applications in which time is measured in a form other than the second and its multiples.


Definition: A day (symbol: d) is an accepted, non-SI unit of time that is defined based on the SI (International System of Units) unit of time, the second, and is equal to 86,400 seconds.

History/origin: The term "day" originates from the Old English term "dæg." It is approximately equal to the period required for the Earth to complete a full rotation with respect to the sun. This was later re-defined in terms of the second in 1960, when the second was redefined in terms of Earth's orbital motion in the year 1900. The second, and therefore the day, was again re-defined in 1967 by atomic electron transition.

Current use: The day is a term used worldwide within many contexts one of the most common of which is to refer to a time interval of 24 hours. It is also used to reference daytime, or the period of time during which the sun is above the horizon. The term also has other colloquial uses such as the day of the week and fixed clock periods like 6:00 am to 6:00 pm, among others.

Second to Day Conversion Table

Second [s]Day [d]
0.01 s1.1574074074074E-7 d
0.1 s1.1574074074074E-6 d
1 s1.15741E-5 d
2 s2.31481E-5 d
3 s3.47222E-5 d
5 s5.78704E-5 d
10 s0.0001157407 d
20 s0.0002314815 d
50 s0.0005787037 d
100 s0.0011574074 d
1000 s0.0115740741 d

How to Convert Second to Day

1 s = 1.15741E-5 d
1 d = 86400 s

Example: convert 15 s to d:
15 s = 15 × 1.15741E-5 d = 0.0001736111 d

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