How many minutes are there in a full day?

The arithmetic is twenty-four hours multiplied by sixty minutes, giving 1,440, and multiplying again by sixty gives 86,400 seconds. The odd-looking base of the calculation is inherited rather than designed. Sixty comes from Babylonian mathematics, which counted in a sexagesimal system, and sixty is convenient because it divides evenly by two, three, four, five, six, ten, twelve, fifteen, twenty and thirty, making thirds and quarters of an hour whole numbers. The twenty-four-hour day comes from Egypt, where day and night were each split into twelve parts. Those parts originally stretched and shrank with the seasons, since daylight is longer in summer, and only became fixed intervals once mechanical clocks made equal hours practical. It is a useful number to hold, because a rate given per day converts to a rate per minute by dividing by 1,440, which comes up constantly in dosage, rainfall and network figures.

A solar day is not exactly 24 hours, which is why leap seconds are occasionally added to keep clocks in step with the Earth's rotation.