Coordinated Universal Time (UTC) is the time standard every clock in the world is measured against. It does not change for daylight saving, which makes it the safest way to record when something happened.
Offsets
A time zone’s offset says how far its local time is from UTC at a given moment. Abuja and Lagos are on UTC+01:00, so when it is 12:00 UTC it is 13:00 in Nigeria. New York is on UTC−05:00 in winter and UTC−04:00 in summer.
Most offsets are whole hours, but not all. India uses UTC+05:30, Nepal uses UTC+05:45 and New Zealand’s Chatham Islands use UTC+12:45 in winter.
Why an offset is not a time zone
An offset is only a snapshot. A time zone is a full set of rules: which offset applies on which dates, when daylight saving starts and ends, and how those rules have changed historically. That is why WhatxTime stores each city’s IANA time zone identifier, such as Europe/London, rather than a fixed number like “+1”. London is UTC+00:00 in January and UTC+01:00 in July, and the identifier captures both.
Writing times unambiguously
- For systems and logs, store times in UTC and convert for display.
- For people, say the city: “09:00 in Lagos” is clearer than “09:00 WAT”, because abbreviations are reused around the world.
Try it yourself with the time zone converter.