Time in Oregon

Most of Oregon lies in the Pacific Time Zone (shown in blue), except for the northern part of Malheur County (shown in purple), which is in the Mountain Time Zone.

Time in Oregon is divided into two zones. The vast majority of the state is contained in the Pacific Time Zone. Most of sparsely populated Malheur County, including its largest city, Ontario, and its county seat, Vale, are in the Mountain Time Zone due to their proximity to Boise, Idaho. The time zone division occurs at the southwest corner of township 35 S, range 37 E (approximately 42.45 degrees north latitude), continuing east to the state line.^[1]

IANA time zone database

In the IANA time zone database, Oregon is contained in two zones:

c.c.*	coordinates*	TZ*	comments*	UTC offset	UTC offset DST	Note
US	[phone]	America/Los_Angeles	Pacific Time	−08:00	UTC−07	All except northern 3/4 of Malheur County
US	[phone]	America/Boise	Mountain Time - south Idaho & east Oregon	−07:00	UTC−06	Northern 3/4 of Malheur County only

References

1. 49 C.F.R. 71.9: Boundary line between mountain and Pacific zones. Accessed June 25, 2012