Convert CST to UTC

Does the difference change during the year?

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

Converting CST to UTC by hand

With the fixed offsets, add 6 hours: 3:30 PM CST is 9:30 PM UTC.

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

Going back from UTC to CST, do the opposite.

Reading a UTC timestamp as CST time

Logs, APIs and flight plans usually carry UTC. A timestamp ending in Z is UTC, and one ending in an offset already says how far from UTC it is. These two name the same moment:

• 2027-01-15T20:00:00Z
• 2027-01-15T14:00:00-06:00

The offset in the second form is the one in force on that date (January 15, 2027). A program should store the UTC form and apply the right offset when it displays the time, rather than storing a local time and hoping the offset is still the same.

What CST and UTC 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.

Coordinated Universal Time

UTC is the world’s reference time. It has no daylight saving time and no seasons: every UTC offset you see (UTC−5, UTC+5:30) is measured from it.