Interstate Highway Time Zone Crossings

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 be 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 changes 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

Bonus Roads(9)

  • 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.

Vale to Pensacola

We’re in that wonderful time of the year when people are still getting used to Daylight Saving Time (that’s Saving without an "s" and no I don’t know why that bothers me). On Twelve Mile Circle that also means I’m getting an odd little bump in traffic that only happens when the time changes either forward or back. It’s a traffic pattern I observe on many of my time zone pages, but is perhaps most prevalent and best described on Arizona Does Not Recognize Daylight Saving Time. Here’s the latest result:

Web Traffic at Time Change
Can you guess when the time changes take place?

I found another fascinating anomaly on the United States timezone map as I was contemplating the recent Spring Forward. Maybe you can too. Go ahead, take a look and let the patterns sink in.

Source: United States National Atlas

I think I’ve probably covered just about every timezone oddity on this map in previous posts but there’s at least one more. Ponder the situation I’m about to describe, but feel free to go back to the map and cheat if you want some assistance: A west coast state bordering the Pacific Ocean has a time zone that’s only one hour different than an east coast state on the Atlantic Ocean. What are the two states?

Vale, OR to Pensacola, FL

The answer is Oregon and Florida, which sounds improbable until one takes a look at the map. Now the answer is probably jumping out in flashing obviousness. Most of Oregon follows Pacific Time but a small chunk of its eastern flank falls with Mountain Time. Conversely, most of Florida follows Eastern Time but the western portion of the panhandle falls within Central Time.

Thus, a person picking up a phone in the town of Vale, in Malheur County, Oregon who wants to call someone in Pensacola, Florida, will only have to worry about a one hour time difference. These two points are nearly 2,500 miles apart and yet have this odd connection because of the double anomaly. If our fictional callers stand just a few miles further apart, the will have to worry about a three hour time difference.

The reason these two small sections of their respective states fall within different time zones has been discussed in previous entries but I’ll provide a brief summary here. Southeastern Oregon has an affinity with Idaho, closer in distance and culture to Boise than to Portland. Conversely, Pensacola has more in common with Mobile than Miami. It’s natural that they don’t follow the time of their home states.

USA Time Zone Anomalies, Part I

Matthew of the prullmw blog[1] is a regular reader and commentator on the Twelve Mile Circle. Recently he wondered whether I might have an interest in time zone boundaries. Indeed I do!

I mentioned the whole Arizona, Navajo, Hopi complexity in my response, but I’d been unable to find a decent map to get the point across. Mapquest provides time zone boundaries at its higher-level views but those disappear just as I click-down to the proper level of detail. The other online mapping sites provide no help either, and the static maps are entirely hit-or-miss. It shouldn’t be this difficult to find a good time zone map but apparently that’s the case unless one wants coverage of the entire United States.

Finally I found a map that demonstrates my point. Actually, more specifically, I made a map. I went to the National Atlas of the United States, applied a time zone layer and dropped the resulting image into graphics software to affix the proper labels. Thanks goodness for taxpayer supported public-domain images. Here’s the result, as edited:

Time Zones in Northeastern Arizona

The boundaries of the Hopi Nation are enclosed entirely within the boundaries of the Navajo Nation. The Navajo Nation has an exclave, Jeddito, within the primary Hopi territory. Likewise the Hopi Nation also has an exclave, Moenkopi, within the Navajo Nation. A major Navajo town with more than 8,000 inhabitants, Tuba City, sits just above Moenkopi north of the intersection of Routes 160 and 264. The Navajo Nation recognizes daylight saving time (DST). Arizona and the Hopi Nation do not. All is fine during the winter months when everyone observes Mountain Standard Time but it spirals into confusion when DST kicks-in.

Imagine someone traveling from Jeddito on Route 264 to Tuba City during the summer. This is not far-fetched. Undoubtedly this happens all the time. Our fictional traveler would start in DST (Jeddito, Navajo exclave), switch to standard time (Hopi), switch to DST (Navajo), switch to standard time (Moenkopi, Hopi exclave) and switch to DST (Navajo) at Tuba City. In reality our traveler wouldn’t actually change his watch four times along this 90 mile route but it’s still a fun set of circumstances to ponder. Plus the lines aren’t even as clean as suggested. For instance, many businesses in Tuba City observe standard time just like the rest of Arizona for commercial reasons and to avoid confusing tourists.

You can find more information about Arizona time zones on a couple of other places on my website if you’re interested:

Matthew brought another fun time zone anomaly to my attention and it’s definitely worth discussing. He suggested I check out the land just south of Grangeville, Idaho. This one is awesome!

Idaho's Time Zone Anomaly

Much of northern Idaho follows Pacific Time which makes sense from an affinity perspective. Residents of Coeur d’Alene are located over four hundred miles away from Boise, the state capital. However they’re only thirty miles away from Spokane, Washington. It’s natural that they would want to align with Pacific Time like their nearby neighbors and cohorts in Washington rather than the Mountain Time observed downstate, and indeed that’s the case.

The time zone boundary crossing Idaho doesn’t follow a straight path. Exact lines don’t make much sense in a rugged, wilderness area. Rather, the boundary snakes along natural features, primarily the Salmon River, as it courses between Oregon and Montana. Either you’re standing on one side of the river or the other. You know what time to expect. Easy.

Rivers, being what they are, follow underlying terrain in search of an outlet. This creates a little hernia of Mountain Time protruding into Pacific Time along the western edge of Idaho. Right here it’s possible to travel due east and move into a later time zone. Generally one has to turn the clock forward when crossing a time zone boundary heading east, but not here. For within this anomaly, this little knob created by the Salmon River, the exact opposite holds true. One turns the clock back.

View Larger Map

The Time Zone Bridge sits a couple of miles outside of Riggins, Idaho, a town found within the anomaly. Cross the little bridge heading northeast, and pay attention to the sign. You’ve transitioned into Pacific Time!

Thanks, Matthew, for that amazing fact. Also check out Part II for even more time zone anomalies in the United States.

[1]Currently in hibernation but I look forward to when he starts reporting on his Goals for 2009, some of which involve geography quests!