Convert CST to BST

Does the difference change during the year?

As written, no: CST is always UTC−6 and BST is always UTC+1, so the gap is 7 hours on every date. But Chicago uses CST only in winter and the UK uses BST only in summer, and people often keep writing “CST” when they mean the local time. Between the local clocks of Chicago and the UK, the gap is 6 hours or 5 hours:

Converting CST to BST by hand

With the fixed offsets, add 7 hours: 3:30 PM CST is 10:30 PM BST.

With the +6 h gap (Jan 1 – Mar 14, Mar 28 – Oct 31, Nov 7 – Dec 31), add 6 hours: 3:30 PM CST is 9:30 PM BST.

With the +5 h gap (Mar 14 – Mar 28, Oct 31 – Nov 7), add 5 hours: 3:30 PM CST is 8:30 PM BST.

Going back from BST to CST, do the opposite.

Where the CST and BST working days overlap

CST to BST (+7 h): Two 9:00–17:00 days share 1 hour: 9:00 AM to 10:00 AM CST, which is 4:00 PM to 5:00 PM BST. That is tight. Put a recurring call at the start of the window, so a meeting that runs late does not push it out.

+6 h (from Jan 1 to Mar 14 and Mar 28 to Oct 31 and Nov 7 to Dec 31, 2027): Two 9:00–17:00 days share 2 hours: 9:00 AM to 11:00 AM CST, which is 3:00 PM to 5:00 PM BST. That is tight. Put a recurring call at the start of the window, so a meeting that runs late does not push it out.

+5 h (from Mar 14 to Mar 28 and Oct 31 to Nov 7, 2027): Two 9:00–17:00 days share 3 hours: 9:00 AM to 12:00 PM CST, which is 2:00 PM to 5:00 PM BST.

A meeting fixed in one city’s calendar moves by an hour for the other when the gap changes. Calendar apps handle this when the event is saved in a named zone (for example America/Chicago) rather than as a fixed offset.

What CST and BST mean

Central Standard Time

CST here is North American Central Standard Time, UTC−6: winter time in Chicago, Houston and Dallas, and all-year time in Mexico City, most of Central America and Saskatchewan. Since 2026 Alberta and the Northwest Territories also stay on UTC−6 all year.

CST can also mean China Standard Time (UTC+8, China) or Cuba Standard Time (UTC−5, Cuba). This page uses Central Standard Time, the meaning people searching for this conversion have in mind. For another one, type the city into the time zone converter.

British Summer Time

BST is UTC+1, the UK’s summer time, from 1:00 AM GMT on the last Sunday of March to 1:00 AM GMT on the last Sunday of October (Summer Time Act 1972 as amended in 2002). In winter the UK is on GMT, UTC+0.