How many seconds are in a day?
Day
86 400
A day, a unit of time, is approximately the period of time during which the Earth completes one rotation around its axis with respect to the Sun (solar day).[1][2] In 1960, the second was redefined in terms of the orbital motion of the Earth in year 1900, and was designated the SI base unit of time. The unit of measurement "day", was redefined as 86 400 SI seconds and symbolized d. In 1967, the second and so the day were redefined by atomic electron transition.[3] A civil day is usually 86 400 seconds, plus or minus a possible leap second in Coordinated Universal Time (UTC), and   occasionally plus or minus an hour in those locations that change from or to daylight saving time.