Not even all of the US participates:
Daylight Saving Time, for the U.S. and its territories, is NOT observed in Hawaii, American Samoa, Guam, Puerto Rico, the Virgin Islands, most of the Eastern Time Zone portion of the State of Indiana, and the state of Arizona (not the Navajo Indian Reservation, which does observe). Navajo Nation participates in the Daylight Saving Time policy, due to its large size and location in three states.
To further complicate things (from
http://www.mccsc.edu/time.html):
the Hopi Partitioned Land, which lies in the midst of the Navajo reservation, follows the the Arizona standard, remaining on Mountain Standard Time year round.
So most of the US follows DST, except for Arizona, which doesn't, except for the Navajo Reservation, which does, except for the Hopi Land, which doesn't. Clear?