It looks like the database has incorrect time for Zone America/Detroit during 1968. In Shanks it is standard time through all of 1968 (and that is also given in the database), but newspaper articles from that same year seem to contradict that. Basically, it seems that Michigan did observe DST the same dates as the rest of the US in 1968. (Maybe with the exception of Berrien county, I have not investigated this exception further since it is before 1970). One source is the Daily Globe, Friday, November 1, 1968 (in Ironwood, Michigan), it has an article written by the AP: (page 14, "Confusion Abounds Over Simple Daylight Time Vote"): Relevant quote from that article: "as a result Michigan has gone on savings time this summer and last." Longer excerpt telling more about the background: The Federal Uniform Time Act of 1966 gave any state permission to exempt itself from fast time if it acted before April 29, 1967, using its normal legislative process to enact an exemption law. Michigan did that. In 1967 the Legislature approved and Gov. George Romney signed a bill providing that all of Michigan would remain year around on Eastern Standard Time, as most of it had since the 1940s. The Citizens Research Council of Michigan says Hawaii was the only other state to pass such an exemption, although Kentucky and Alaska were granted temporary exemptions. Backers of savings time, however, circulated referendum petitions challenging the exemption law and succeeded in putting it on the ballot. Then: success suspended the law, and as a result Michigan has gone on savings time this summer and last. Snarled up with the Daylight Tune issue is another section of the Uniform Time Act which put all of Michigan's Lower Peninsula on Eastern Time and the entire Upper Peninsula on Central Time. The two eastern counties of the U.P. have ignored the law and observe Eastern Standard and Eastern Daylight Time like the Lower Peninsula. Best regards, Steffen Thorsen - timeanddate.com