America/Phoenix

Time zone identifier: America/Phoenix

Current civil offset: -07:00 (MST)

Current DST state: Observing Standard Time

First standard time adoption: Adopted on 1883-11-18

Local Mean Time (LMT): -07:28:18 based on geographic meridian

Total recorded transitions: 11 transitions across 3 distinct offsets

Associated countries: CA, US

Aliases (Link targets): America/Creston, MST, US/Arizona

Historical Offset Step Chart (1880 to Present)

Text summary: America/Phoenix shifted between 3 distinct offsets from 1883-11-18 through the modern era.

Complete Transition History (11 Transitions)

UTC Instant	Local Wall Time	Shift	Abbreviation	DST	Effect
`1883-11-18T19:00:00Z`	`1883-11-18 12:00:00`	-07:28:18 → -07:00	`MST`	No	gap
`1918-03-31T09:00:00Z`	`1918-03-31 03:00:00`	-07:00 → -06:00	`MDT`	Yes	gap
`1918-10-27T08:00:00Z`	`1918-10-27 01:00:00`	-06:00 → -07:00	`MST`	No	overlap
`1919-03-30T09:00:00Z`	`1919-03-30 03:00:00`	-07:00 → -06:00	`MDT`	Yes	gap
`1919-10-26T08:00:00Z`	`1919-10-26 01:00:00`	-06:00 → -07:00	`MST`	No	overlap
`1942-02-09T09:00:00Z`	`1942-02-09 03:00:00`	-07:00 → -06:00	`MWT`	Yes	gap
`1944-01-01T06:01:00Z`	`1943-12-31 23:01:00`	-06:00 → -07:00	`MST`	No	overlap
`1944-04-01T07:01:00Z`	`1944-04-01 01:01:00`	-07:00 → -06:00	`MWT`	Yes	gap
`1944-10-01T06:01:00Z`	`1944-09-30 23:01:00`	-06:00 → -07:00	`MST`	No	overlap
`1967-04-30T09:00:00Z`	`1967-04-30 03:00:00`	-07:00 → -06:00	`MDT`	Yes	gap
`1967-10-29T08:00:00Z`	`1967-10-29 01:00:00`	-06:00 → -07:00	`MST`	No	overlap

Notes from the Maintainers

Source: northamerica (Lines 797 to 821)

Now we turn to US areas that have diverged from the consensus since 1970.

Arizona mostly uses MST.

From Paul Eggert (2002-10-20):

The information in the rest of this paragraph is derived from the
Daylight Saving Time web page
<http://www.dlapr.lib.az.us/links/daylight.htm> (2002-01-23)
maintained by the Arizona State Library, Archives and Public Records.
Between 1944-01-01 and 1944-04-01 the State of Arizona used standard
time, but by federal law railroads, airlines, bus lines, military
personnel, and some engaged in interstate commerce continued to
observe war (i.e., daylight saving) time.  The 1944-03-17 Phoenix
Gazette says that was the date the law changed, and that 04-01 was
the date the state's clocks would change.  In 1945 the State of
Arizona used standard time all year, again with exceptions only as
mandated by federal law.  Arizona observed DST in 1967, but Arizona
Laws 1968, ch. 183 (effective 1968-03-21) repealed DST.

Shanks says the 1944 experiment came to an end on 1944-03-17.
Go with the Arizona State Library instead.

Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]

Attributed Statements:

Paul Eggert (2002-10-20):

The information in the rest of this paragraph is derived from the Daylight Saving Time web page <http://www.dlapr.lib.az.us/links/daylight.htm> (2002-01-23) maintained by the Arizona State Library, Archives and Public Records. Between 1944-01-01 and 1944-04-01 the State of Arizona used standard time, but by federal law railroads, airlines, bus lines, military personnel, and some engaged in interstate commerce continued to observe war (i.e., daylight saving) time. The 1944-03-17 Phoenix Gazette says that was the date the law changed, and that 04-01 was the date the state's clocks would change. In 1945 the State of Arizona used standard time all year, again with exceptions only as mandated by federal law. Arizona observed DST in 1967, but Arizona Laws 1968, ch. 183 (effective 1968-03-21) repealed DST. Shanks says the 1944 experiment came to an end on 1944-03-17. Go with the Arizona State Library instead. Zone NAME STDOFF RULES FORMAT [UNTIL]

Years on Record

Methodology Note: The 1970 Rule

tzdb guarantees accuracy for timestamps from 1970 onwards. Transitions prior to 1970 represent best-effort historical reconstructions.