Boundary guides

Each guide quotes the legal line in 49 CFR Part 71 and then lists the counties the boundary sample actually placed on each side.

• 49 CFR 71.5Central–Eastern Time Zone LineThe legal line between Central and Eastern Time, from Lake Superior through Indiana, Kentucky, Tennessee, and the Florida Panhandle, with the counties on each side.
• 49 CFR 71.7Central–Mountain Time Zone LineHow 49 CFR 71.7 divides Central and Mountain Time across the Dakotas, Nebraska, Kansas, and far West Texas.
• 49 CFR 71.9Mountain–Pacific Time Zone LineThe Salmon River split in Idaho, Malheur County in Oregon, and the West Wendover exception on the Nevada line.
• IndianaIndiana Time Zone MapWhich Indiana counties are Central Time, which are Eastern, and why the whole state now observes daylight saving time.
• ArizonaArizona Daylight Saving TimeWhy most of Arizona stays on Mountain Standard Time, and where the Navajo Nation and the Hopi reservation differ.
• KentuckyKentucky Time ZonesWhich side of Kentucky is Eastern Time, which side is Central, and how 49 CFR 71.5(c) draws the line.
• TennesseeTennessee Time ZonesEastern versus Central Time in Tennessee, including where 49 CFR 71.5(d) passes Scott, Morgan, Roane, Rhea, and Hamilton counties.
• FloridaFlorida Time ZonesWhich Florida Panhandle counties are Central Time, and how Gulf County is split by the Apalachicola River.
• TexasTexas Time ZonesEl Paso and Hudspeth counties are Mountain Time. The other 252 Texas counties are Central Time.
• MichiganMichigan Time ZonesFour Upper Peninsula counties are Central Time. The rest of Michigan, including Detroit, is Eastern.
• Idaho and OregonIdaho and Oregon Time Zone LinePacific Time in northern Idaho, Mountain Time south of the Salmon River, and the Malheur County split in Oregon.
• 49 CFR 71.12Hawaii-Aleutian TimeHawaii does not observe daylight saving time. The Aleutians west of 169°30′ W do, under the same legal zone name.
• Northern PlainsDakota and Nebraska Time ZonesWhere Mountain Time starts in North Dakota, South Dakota, and Nebraska, including counties the Missouri River and the Sandhills line actually split.