Recently the Senate passed a bill that would make Daylight Savings Time (or DST) permanent by unanimous consent. (and its passage even surprised some Senators) But even though we may gripe twice a year about the sudden time changes, would making DST permanent be a good thing?

Back in 2015, Andy Woodruff took a deeper look into DST and mapped out how the time changes affect sunrise and sunset times across the United States. Depending on your preferences you could actually love it or hate it. Andy’s Should You Hate Daylight Savings Time infographic uses “reasonable” Sunrise time at 7:00 AM or earlier and “reasonable” sunset time of 6:00 PM or later. However, you can interact with his maps and create your own “reasonable” times to find out where you stand.

Latitude affects how early or late the sun rises and sets, but what the clock says depends on a location’s longitude within its time zone. The farther east it is, the earlier the sun will rise and set. Considering all this, I want to map sunrise and sunset times in the United States and see how they are affected by daylight saving time. I’ve done so by using a little bit of GIS and the super handy SunCalc JavaScript library by Vladimir Agafonkin.

Let’s map how many days of the year have reasonable sunrise and sunset times with and without daylight saving time. I define “reasonable” times as 7 AM and 6 PM. That’s kind of arbitrary, but assuming roughly half an hour of twilight, it at least puts some light in the sky around the time the average American wakes up (6:30ish based on some cursory poking around) and at the end of the business day. But you can define them differently. Explore the coarsely gridded map below and see the geography of sunrise and sunset with and without daylight saving time.

To summarize, these are the scenarios using my preferred times.

In 2019, Andy created an updated Daylight Saving Time Gripe Assistant Tool so you could evaluate the benefits of DST based on where you live, and your preferences for sunrise and sunset.

NOTE: As you can see in the default preferences of the tool, by far most of the country would benefit from abolishing DST instead of making permanent.