CST to GMT
Chicago to London.
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All date & timeQuestions
What time is GMT when it is 12:00 CST?
18:00. Greenwich Mean Time is 6 hours ahead of Central Time, all year round. A 9-to-5 day in Chicago overlaps a 9-to-5 day in London for 2 hours, between 09:00 and 11:00 CST.
Is the difference between CST and GMT the same all year?
Yes. Greenwich Mean Time is 6 hours ahead of Central Time, all year round. Both zones change their clocks, and close enough to the same dates that the gap between them holds — apart from a week or two each spring and autumn when one has shifted and the other has not.
What do CST and GMT actually stand for?
CST is Central Time, the zone covering Chicago, currently UTC−6 in January. GMT is Greenwich Mean Time, covering London, at UTC+0. The most overloaded abbreviation in scheduling: CST is also China Standard Time, which is fourteen hours away from this one. If a message says CST and mentions a colleague in Shanghai, it does not mean Chicago.
Anything worth knowing about Greenwich Mean Time?
GMT and UK time are the same thing only in winter. From late March to late October London runs on British Summer Time, an hour ahead of GMT, so a meeting booked as 'GMT' with someone in London is an hour out for most of the year.
When is a good time to call between Chicago and London?
A 9-to-5 day in Chicago overlaps a 9-to-5 day in London for 2 hours, between 09:00 and 11:00 CST. If the call has to happen outside that, the fairer arrangement is usually to alternate which side takes the awkward hour rather than always asking the same one.
How it works, and more about cst → gmt
The difference, and whether you can rely on it
In January, Greenwich Mean Time is 6 hours ahead of Central Time — UTC−6 against UTC+0. It stays that way all year, so the number is worth memorising if you work across these two often.
When you can both be at a desk
A standard working day in Chicago overlaps one in London between 09:00 and 11:00 CST — 2 hours. Anything outside that asks somebody to start early or finish late.
Reading the abbreviations literally will mislead you
CST strictly means one fixed offset, but almost nobody uses it that way. People write it to mean the time in Chicago, which shifts if that city observes daylight saving — and it does. This page follows the common usage rather than the strict one, because the strict reading gives an answer that is wrong for a good part of the year.
The most overloaded abbreviation in scheduling: CST is also China Standard Time, which is fourteen hours away from this one. If a message says CST and mentions a colleague in Shanghai, it does not mean Chicago. GMT and UK time are the same thing only in winter. From late March to late October London runs on British Summer Time, an hour ahead of GMT, so a meeting booked as 'GMT' with someone in London is an hour out for most of the year.
Scheduling something recurring
For a one-off, the converter above is the whole job. For a standing meeting across zones it is worth putting the invitation in a calendar that stores the zone rather than the time — then the changeover is handled for you and nobody has to remember. If you are trying to find a slot across more than two places at once, the meeting planner shows a whole day at a glance instead.