See also: List of counties in Idaho. The U.S. state of Idaho is covered by two time zones, as described below. All locations observe daylight saving time.
The Pacific Time Zone (DST) covers an area roughly coterminous with the Idaho Panhandle or North Idaho:
An easy way to distinguish the line is that it essentially follows the line that divides Washington and Oregon. Idaho counties east of Washington observe Pacific Time, and Idaho counties east of Oregon observe Mountain Time.
The Mountain Time Zone (DST) covers the rest of the state.
The 1918 Standard Time Act put most of Idaho into the Pacific Time Zone - only the very eastern parts were in the Mountain Time Zone.[1]
For three decades or so in the middle of the twentieth century, Shoshone County had its own time arrangements; it was said to be "on permanent daylight time",[2] so that in the winter the county had the same clock time as Montana and southern Idaho, but in the summer it had the same clock time as Spokane and northern Idaho.
The tz database version contains two time zones for Idaho: