America/Puerto_Rico

Time zone identifier: America/Puerto_Rico

Current civil offset: -04:00 (AST)

Current DST state: Observing Standard Time

First standard time adoption: Adopted on 1899-03-28

Local Mean Time (LMT): -04:24:25 based on geographic meridian

Total recorded transitions: 4 transitions across 3 distinct offsets

Associated countries: AG, AI, AW, BL, BQ, CA, CW, DM, GD, GP, KN, LC, MF, MS, PR, SX, TT, VC, VG, VI

Aliases (Link targets): America/Anguilla, America/Antigua, America/Aruba, America/Blanc-Sablon, America/Curacao, America/Dominica, America/Grenada, America/Guadeloupe, America/Kralendijk, America/Lower_Princes, America/Marigot, America/Montserrat, America/Port_of_Spain, America/St_Barthelemy, America/St_Kitts, America/St_Lucia, America/St_Thomas, America/St_Vincent, America/Tortola, America/Virgin

Historical Offset Step Chart (1880 to Present)

Text summary: America/Puerto_Rico shifted between 3 distinct offsets from 1899-03-28 through the modern era.

Complete Transition History (4 Transitions)

UTC Instant	Local Wall Time	Shift	Abbreviation	DST	Effect
`1899-03-28T16:24:25Z`	`1899-03-28 12:24:25`	-04:24:25 → -04:00	`AST`	No	gap
`1942-05-03T04:00:00Z`	`1942-05-03 01:00:00`	-04:00 → -03:00	`AWT`	Yes	gap
`1945-08-14T23:00:00Z`	`1945-08-14 20:00:00`	-03:00 → -03:00	`APT`	Yes	offset-only
`1945-09-30T05:00:00Z`	`1945-09-30 01:00:00`	-03:00 → -04:00	`AST`	No	overlap

Notes from the Maintainers

Source: northamerica (Lines 3809 to 3829)

Anguilla
Antigua & Barbuda
Aruba
Caribbean Netherlands
Curaçao
Dominica
Grenada
Guadeloupe
Montserrat
Puerto Rico
St Barthélemy
St Kitts-Nevis
Sint Maarten / St Martin
St Lucia
St Vincent & the Grenadines
Trinidad & Tobago
Virgin Is (UK & US)

There are too many San Juans elsewhere, so we'll use 'Puerto_Rico'.
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.