Is UTC the same as GMT?

They usually line up to the second in casual use, but UTC is a standard kept by atomic clocks while GMT is a time zone. Systems and standards refer to UTC.

Why should I store times in UTC?

Storing UTC avoids ambiguity from time zones and daylight saving. Convert to a local zone only when displaying the time to a person.

Does the time zone converter upload anything?

No. Conversions happen locally in your browser and nothing is uploaded.

Explainer1 min readUpdated June 29, 2026

What is UTC, and how do time zones work?

Short answer

UTC (Coordinated Universal Time) is the worldwide time standard. Every time zone is described as an offset from UTC, such as UTC+1 or UTC-5. Local clocks are just UTC shifted by that offset, sometimes adjusted again for daylight saving time.

One reference, many offsets

Rather than every region keeping its own independent clock, the world agrees on one reference, UTC, and defines local times as offsets from it. New York in winter is UTC-5; Berlin is UTC+1. Convert both to UTC and you can compare them directly.

12:00 UTC  =  07:00 in New York (UTC-5)
12:00 UTC  =  13:00 in Berlin   (UTC+1)

The same instant in two zones

Try it: Time Zone ConverterConvert a time between zones locally, using UTC as the common reference.Open tool

Daylight saving complicates offsets

Many regions shift their clocks forward in summer, so a zone's offset is not fixed all year. New York is UTC-5 in winter but UTC-4 in summer. This is why storing a time zone name, not just an offset, matters.

UTC vs GMTIn everyday use they are treated as the same, but UTC is a precise time standard based on atomic clocks, while GMT is a time zone. For software, prefer UTC.