Holiday data is acquired from a variety of public and private sources. Wherever possible we attempt to use official government data that’s cross referenced by one or more additional sources. For example, in the US, the U.S. Office of Personnel Management (OPM), which serves as the chief human resources agency and personnel policy manager for the Federal Government, maintains a list of federal holidays. The State of California maintains their own set of holidays, some of which overlap with the federal government’s, and some of which do not. Abstract’s Holiday API identifies and validates all these dates so you don’t have to.

The Holiday API starts with officially-recognized government holidays as its basis for the holiday data. As mentioned above, this data is cross checked with as many other data sources as possible to ensure it's accurate. There are several other categories of holidays, such as religious holidays which may not be observed or only semi-observed by the government. In cases where the given national or state/province does not recognize the holiday, then it does not appear in our Holiday API. However, we are working on enriching our data set with non-observed religious and other such holidays. If you're interested in contributing to or using this data, please contact us.

The countries and territories covered by the API include: Afghanistan, Albania, Algeria, American Samoa, Andorra, Angola, Anguilla, Antarctica, Antigua and Barbuda, Argentina, Armenia, Aruba, Australia, Austria, Azerbaijan, Bahamas, Bahrain, Bangladesh, Barbados, Belarus, Belgium, Belize, Benin, Bermuda, Bhutan, Bolivia, Bosnia and Herzegovina, Botswana, Bouvet Island, Brazil, British Indian Ocean Territory, Brunei Darussalam, Bulgaria, Burkina Faso, Burundi, Cambodia, Cameroon, Canada, Cape Verde, Cayman Islands, Central African Republic, Chad, Chile, China, Colombia, Comoros, Congo, Cook Islands, Costa Rica, Cote D'Ivoire (Ivory Coast), Croatia, Cuba, Cyprus, Czech Republic, Denmark, Djibouti, Dominica, Dominican Republic, East Timor, Ecuador, Egypt, El Salvador, Equatorial Guinea, Eritrea, Estonia, Ethiopia, Falkland Islands (Malvinas), Faroe Islands, Fiji, Finland, France, France, Metropolitan, French Guiana, French Polynesia, French Southern Territories, Gabon, Gambia, Georgia, Germany, Ghana, Gibraltar, Greece, Greenland, Grenada, Guadeloupe, Guam, Guatemala, Guinea, Guinea-Bissau, Guyana, Haiti, Heard and McDonald Islands, Honduras, Hong Kong, Hungary, Iceland, India, Indonesia, Iran, Iraq, Ireland, Israel, Italy, Jamaica, Japan, Jordan, Kazakhstan, Kenya, Kiribati, Korea (North), Korea (South), Kuwait, Kyrgyzstan, Laos, Latvia, Lebanon, Lesotho, Liberia, Libya, Liechtenstein, Lithuania, Luxembourg, Macau, Macedonia, Madagascar, Malawi, Malaysia, Maldives, Mali, Malta, Marshall Islands, Martinique, Mauritania, Mauritius, Mayotte, Mexico, Micronesia, Moldova, Monaco, Mongolia, Montserrat, Morocco, Mozambique, Myanmar, Namibia, Nauru, Nepal, Netherlands, Netherlands Antilles, New Caledonia, New Zealand, Nicaragua, Niger, Nigeria, Niue, Norfolk Island, Northern Mariana Islands, Norway, Oman, Pakistan, Palau, Panama, Papua New Guinea, Paraguay, Peru, Philippines, Pitcairn, Poland, Portugal, Puerto Rico, Qatar, Reunion, Romania, Russian Federation, Rwanda, Saint Kitts and Nevis, Saint Lucia, Saint Vincent and The Grenadines, Samoa, San Marino, Sao Tome and Principe, Saudi Arabia, Senegal, Seychelles, Sierra Leone, Singapore, Slovak Republic, Slovenia, Solomon Islands, Somalia, South Africa, Spain, Sri Lanka, St. Helena, St. Pierre and Miquelon, Sudan, Suriname, Svalbard and Jan Mayen Islands, Swaziland, Sweden, Switzerland, Syria, Taiwan, Tajikistan, Tanzania, Thailand, Togo, Tokelau, Tonga, Trinidad and Tobago, Tunisia, Turkey, Turkmenistan, Turks and Caicos Islands, Tuvalu, Uganda, Ukraine, United Arab Emirates, United Kingdom (Britain / UK), United States of America (USA), US Minor Outlying Islands, Uruguay, Uzbekistan, Vanuatu, Vatican City State (Holy See), Venezuela, Viet Nam, Virgin Islands (British), Virgin Islands (US), Wallis and Futuna Islands, Western Sahara, Yemen, Yugoslavia, Zaire, Zambia, and Zimbabwe.