GMT to CST
London to Chicago.
- Nothing leaves your browser
- Free, no sign-up
Related tools
All date & timeQuestions
What time is CST when it is 12:00 GMT?
06:00. Central Time is 6 hours behind Greenwich Mean Time, all year round. A 9-to-5 day in London overlaps a 9-to-5 day in Chicago for 2 hours, between 15:00 and 17:00 GMT.
Is the difference between GMT and CST the same all year?
Yes. Central Time is 6 hours behind Greenwich Mean 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 GMT and CST actually stand for?
GMT is Greenwich Mean Time, the zone covering London, currently UTC+0 in January. CST is Central Time, covering Chicago, at UTC−6. 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.
Anything worth knowing about Central Time?
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.
When is a good time to call between London and Chicago?
A 9-to-5 day in London overlaps a 9-to-5 day in Chicago for 2 hours, between 15:00 and 17:00 GMT. 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 gmt → cst
The difference, and whether you can rely on it
In January, Central Time is 6 hours behind Greenwich Mean Time — UTC+0 against UTC−6. 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 London overlaps one in Chicago between 15:00 and 17:00 GMT — 2 hours. Anything outside that asks somebody to start early or finish late.
Reading the abbreviations literally will mislead you
GMT strictly means one fixed offset, but almost nobody uses it that way. People write it to mean the time in London, 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.
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. 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.
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.