The timezone AST in Puerto Rico

Only 1 nationwide time zone

UTC	-4
Standard time:	Atlantic Standard Time (AST)
Daylight saving time:	discontinued 1945

Puerto Rico has an east-west extension of 1.9 degrees of longitude. Given the country's location in Caribbean, this corresponds to about 210 kilometers. With such a small extent the course of the sun at different positions in the country hardly matters. The position of the sun in the west of the country deviates from that in the east only about 8 minutes. This means the sun rises and sets 8 minutes later in the west than in the east.


The Atlantic Standard Time also applies in Anguilla, , Aruba, Barbados, in parts of Canada, in Curacao, Dominica, Grenada, Guadeloupe, Antigua and Barbuda, Bonaire, Saint Martin, St. Martin, Martinique, Montserrat, Trinidad and Tobago, Dominican Republic, Saint Barthelemy, Saint Kitts and Nevis, Saint Lucia, Virgin Islands, Saint Vincent and the Grenadines, in parts of Greenland, on the British Virgin Islands and in the Bermudas.

No more daylight saving time in Puerto Rico

Due to the sun's orbit around the equator, the days are longer in summer (June to September in the northern hemisphere). Countries that switch to daylight saving time in the summer months align the daylight phase with the human rhythm. Unused bright morning hours are thus shifted into the evening (more information on daylight saving time here).

Due to the relative proximity to the equator, the impact in Puerto Rico is not particularly large. San Juan is only 2,050 km from the equator. A day in midsummer would then not last from 05:48 to 19:04, but from 06:48 to 20:04. The effect would be quite noticeable in the evening, but the sun rising later in the morning falls at a time when many people are already awake. Thus, in 1945, the decision was made to finally abandon daylight saving time in Puerto Rico.

Changes in Daylight Saving Times

In Puerto Rico Daylight Saving Time has been observed since 1942 until 09/30/1945.