Time Zone History

Chicago time zone history

On standard time, clocks in Chicago run 9 minutes behind local mean solar time. Local mean time, UTC−5:50:36, ended in 1883.

UTC−6

Standard time is UTC−6 (CDT/CST); clocks go forward to UTC−5 on the second Sunday in March and back on the first Sunday in November.

Covers: Central time, most areas · tz database name America/Chicago

Convert a time from Chicago

Summer time in every year since 1970

UTC−6: today’s standard timeUTC−5:50:36: 9 minutes ahead of today’s standard timeUTC−5: 1 hour ahead of today’s standard timeUTC−6: today’s standard timeUTC−5:50:36: 9 minutes ahead oftoday’s standard timeUTC−5: 1 hour ahead of today’sstandard time

How to read this chart

Before 1970

187018901910193019501970187019101950
JanFebMarAprMayJunJulAugSepOctNovDec1970198019902000201020202028JFMAMJJASOND1970198019902000201020202028

Standard time changes

DateChangeNew standard timeClock label
Before 1970
November 18, 1883Local mean time (UTC−5:50:36) replacedUTC−6CST
March 1, 1936Standard time forward 1 hourUTC−5EST
November 15, 1936Standard time back 1 hourUTC−6CST

Daylight saving periods

YearsClocks go forwardClocks go backShift and labels
1918–1919last Sunday in March, 02:00last Sunday in October, 02:001 hour, CST to CDT
1920June 13October 311 hour, CST to CDT
1921March 27October 301 hour, CST to CDT
1922–1935last Sunday in April, 02:00last Sunday in September, 02:001 hour, CST to CDT
1937–1941last Sunday in April, 02:00last Sunday in September, 02:001 hour, CST to CDT
1942February 9not that year1 hour, CST to CWT
1945not that yearSeptember 301 hour
1946–1954last Sunday in April, 02:00last Sunday in September, 02:001 hour, CST to CDT
1955–1973last Sunday in April, 02:00last Sunday in October, 02:001 hour, CST to CDT

Since 1970: the periods shared by 5 of 29 zones, listed on the United States page.

Clock changes in 2026, 2027 and 2028

The clocks go forward 1 hour (CST to CDT) on March 8, 2026, March 14, 2027 and March 12, 2028 at 02:00 and back 1 hour (CDT to CST) on November 1, 2026, November 7, 2027 and November 5, 2028 at 02:00, local time.

Also on UTC−6

Knox, Indiana (United States), Menominee (United States), Tell City, Indiana (United States), New Salem, North Dakota (United States), Center, North Dakota (United States), Beulah, North Dakota (United States), Regina (Canada), Swift Current (Canada), Matamoros (Mexico) and Ojinaga (Mexico) (nearest first; 17 more on the list of offsets).

Clocks next door since 1970

  • Knox, Indiana (105 km): same time except 2,374 days in 1991–2006.
  • Winamac, Indiana (124 km): usually 1 hour ahead; different on 7,399 days in 1970–2026.
  • Indianapolis, Indiana (263 km): usually 1 hour ahead; different on 7,056 days in 1970–2026.
  • Vincennes, Indiana (353 km): usually 1 hour ahead; different on 7,637 days in 1970–2026.
  • Menominee (362 km): same time except 661 days in 1970–1973.

How it compares

Standard time has stayed at UTC−6 since 1936.