UTC stands for Coordinated Universal Time, which is the primary time standard by which the world regulates clocks and time. It is a 24-hour time standard that is kept using highly precise atomic clocks combined with the Earths rotation. UTC is within about one second of mean solar time at 0° longitude and is not adjusted for daylight saving time. It is used to set all time zones around the world. UTC is based on International Atomic Time (TAI) with leap seconds added at irregular intervals to compensate for the accumulated difference between TAI and time measured by Earths rotation. Leap seconds are inserted as necessary to keep UTC within 0.9 seconds of the UT1 variant of universal time.

UTC is used in many Internet and World Wide Web standards, and the Network Time Protocol (NTP) transmits time information from the UTC system. Clients can obtain the current UTC from a number of official internet UTC servers, and for sub-microsecond precision, clients can obtain the time from satellite signals. UTC is the time standard commonly used across the world, and the worlds timing centers have agreed to keep their time scales closely synchronized - or coordinated - therefore the name Coordinated Universal Time.

To convert UTC to local time, one needs to know the time difference between UTC and their time zone. Standard time within most time zones is a certain whole number of hours offset from Coordinated Universal Time (UTC), maintained by a large number of very precise “atomic clocks” kept at laboratories around the world. For example, if someone lives in Houston, Texas, which is in United States Central Standard Time, to convert 18:00 UTC (6:00 p.m.) into their local time, they need to subtract 6 hours, to get 12 noon CST. During daylight saving (summer) time, they would only subtract 5 hours, so 18:00 UTC would convert to 1:00 p.m CDT.