Definition:Time/Unit/Day

Definition

$\ds $

$\ds 1$

day

$\ds $

$=$

$\ds 24$

hours

$\ds $

$=$

$\ds 60 \times 24$

$\ds = 1440$

minutes

$\ds $

$=$

$\ds 60 \times 60 \times 24$

$\ds = 86\, 400$

seconds

The symbol for the day is $\mathrm {day}$ or $\mathrm d$.

The day as defined here is also known as a mean solar day so as to distinguish it from the sidereal day.

Until $1967$, when the second was redefined to be the SI base unit of time, the day was the fundamental unit of time.

It was defined as being the length of time it takes the Earth to rotate once on its axis relative to the sun.