I’ve been noticing search engine queries lately seeking additional information about points along US Interstate Highways where travelers cross from one time zone into another. I’m going to do that myself soon on my upcoming trip and I couldn’t find a comprehensive resource either. Maybe there’s one out there hidden away in a lonely corner of the Intertubes. Maybe not. I didn’t see it so I decided to create my own. Hopefully others will find this compact reference useful too.
Yes, I understand that mobile phones and other networked devices grab time changes automatically without human intervention from nearby cell towers as one drives merrily down the highway. However some of us like to by hyper-prepared before embarking on a journey. I even recorded the lat/long coordinates so travelers (OK, maybe just me…) could drop the waypoints into their GPS receivers and know exactly where the time change would happen well in advance.
View Interstate Highway Time Zone Changes in a larger map
Readers will want to open this map in another tab or window. It’s not very useful in its present scaled down version that is included for illustrative purposes. Others may prefer the even more detailed Google spreadsheet with links that I prepared. The spreadsheet layout mimicked the geographic footprint of the United States in rough terms, for example I positioned Idaho at the top-left (northwest) and Florida at the bottom-right (southeast). That was also the reason why Interstate numbers on the spreadsheet and the lists below were ordered from large to small (I-94 to I-8). I didn’t reverse the order just to be obstinate. Even-numbered Interstates run roughly west to east across the nation with the 2-digit numbering increasing from south to north. There were also a handful of odd-numbered highways that crossed time zone boundaries too and muddied the construct a bit. Again, the rules applied in general terms only.
This exercise was a lot more tedious than I imagined. Believe me, I’d use much more colorful language if this wasn’t a family-friendly website. I’d assumed quite foolishly that the preponderance of time changes would happen at state borders, and simplify my task. Some do, although many more switch at random county borders which were much more difficult to pinpoint on a map. That’s why I think people have trouble tracking time zones as they drive. Now they have a tool — this page.
Here’s what I found. I’m sure errors or omissions crept into this because it was such a pain to compile. Please let me know and I’ll make corrections.
Change Between Pacific Time and Mountain Time
- Interstate 90: Idaho <--> Montana
- Interstate 84: Baker Co., OR <--> Malheur Co., OR
- Interstate 80: Unincorporated Elko Co., NV <--> West Wendover, Elko Co., NV(1)
- Interstate 40: California <--> Arizona (Standard Time); Eastern Arizona <--> SE corner of Navajo Reservation in AZ (Daylight Saving Time)(2)(3)
- Interstate 15: Nevada <--> Arizona (Standard Time); Arizona <--> Utah (Daylight Saving Time)(2)
- Interstate 10: California <--> Arizona (Standard Time); Arizona <--> New Mexico (Daylight Saving Time)(2)
- Interstate 08: California <--> Arizona (Standard Time); no change during DST(2)(4)
Change Between Mountain Time and Central Time
- Interstate 94: Stark Co., ND <--> Morton Co., ND
- Interstate 90: Jackson Co., SD <--> Jones Co., SD
- Interstate 80: Keith Co., NE <--> Lincoln Co., NE
- Interstate 70: Sherman Co., KS <--> Thomas Co., KS(5)
- Interstate 40: New Mexico <--> Texas
- Interstate 10: Hudspeth Co., TX <--> Culberson Co., TX
Change Between Central Time and Eastern Time
- Interstate 94: Indiana <--> Michigan
- Interstate 90: LaPorte Co., IN <--> St. Joseph Co., IN(6)
- Interstate 85: Alabama <--> Georgia(7)
- Interstate 80: LaPorte Co., IN <--> St. Joseph Co., IN(6)
- Interstate 74: Illinois <--> Indiana
- Interstate 70: Illinois <--> Indiana
- Interstate 65: Jasper Co., IN <--> White Co., IN /AND/ Hart Co., KY <--> Larue Co., KY(8)
- Interstate 64: Perry Co., IN <--> Crawford Co., IN
- Interstate 59: Alabama <--> Georgia
- Interstate 40: Cumberland Co., TN <--> Roane Co., TN
- Interstate 24: Marion Co., TN <--> Hamilton Co., TN
- Interstate 20: Alabama <--> Georgia
- Interstate 10: Jackson Co., FL <--> Gadsden Co., FL
- Western Kentucky Parkway: Grayson Co., KY <--> Hardin Co., KY(10)
- Cumberland Parkway: Russel Co., KY <--> Pulaski Co., KY(11)
(1) West Wendover is the only part of Nevada that officially observes Mountain Time, primarily so gamblers from Salt Lake City — the nearest large town — won’t have to deal with a time change and can focus on losing their money without distraction. This was described in (West) Wendover: What Time? What State?
(2) Arizona does not recognize Daylight Saving Time, meaning that for practical purposes the spot where the time zone change takes place shifts in the Spring and the Fall. This can sometimes lead to embarrassing situations.
(3) The exception to the "Arizona doesn’t recognize DST rule" is the portion of the sprawling Navajo Nation that crosses into Arizona. The Navajo did this to assert their sovereignty as well as to keep their tri-state Nation on the same time all year.
(4) Interstate 8 extends from San Diego, California to south-central Arizona; fairly short by interstate standards. Therefore it does not experience a time change when the two states observe the same time (i.e, when the Pacific Time Zone switches to DST and Arizona remains on Mountain Standard Time)
(5) I crossed this one during my Dust Bowl trip. See Kansas Mountain Time.
(6) You’re not seeing things. Interstates 80 and 90 are repeated with the same information here. That’s because they’re co-signed at this spot.
(7) Interstate 85 is the best example of an odd-numbered Interstate messing up my chart. The time change happens at a very southern segment of this very eastern highway.
(8) Interstate 65 starts in Central Time in an Indiana suburb of Chicago, switches to Eastern Time as it heads south, then switches back into Central Time in Kentucky
(9) I included Kentucky parkways because they’re significant roads albeit they’re not Interstate highways (not even Secret Interstates). I probably could have added other roads too.
(10) I will be crossing here on an upcoming trip. This was the spot that inspired me to go ahead and compile the list.
(11) I crossed here in the summer of 2013 during my Kentucky Adventures.