Time conversion Time units are used to measure and describe the duration or interval of time between two events or points in time. The second is the most commonly used time unit. The second is the base unit of time in the International System of Units (SI). In everyday life, the second is used to measure the duration of short events or intervals. A millisecond is a unit of time that is equal to one thousandth of a second, or 0.001 second. In sports timing, such as in track and field events, the difference between the first and second place finisher can sometimes be determined by milliseconds, highlighting the importance of accurate and precise timekeeping. An hour is a unit of time that is commonly used to measure the duration of time periods, and it is equal to 60 minutes. One hour can also be divided into 3 600 seconds. A day is a unit of time that is equivalent to 24 hours, 1 440 minutes or 86 400 seconds. It is defined as the time it takes for the Earth to complete one rotation on its axis. Here are some units of time: second (s), minute (min), hour, day (d), week, month, year, decade, century (cent), millennium. Below are various time unit conversions: Convert milliseconds to seconds Convert seconds to milliseconds