a period of time equal to 60 seconds; one sixtieth of an hour.
Second is the time interval equal to 9192631770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom
An hour is a unit of time conventionally reckoned as 1⁄24 of a day and scientifically reckoned as 3,599–3,601 seconds
A day is the approximate time it takes for the Earth to complete one rotation. It is defined as exactly 86,400 seconds.
A century is a period of 100 years.
A month is 1/12th of a year. In the Gregorian calendar, an average month has exactly 30.436875 days. It was originally based on the time it takes for the moon to rotate the Earth.
A week is a period of 7 days.
In the Gregorian calendar, a year has on average 365.2425 days. It is based on the amount of time it takes for the Earth to rotate the sun..
A decade is a period of 10 years.