You could use external Holiday API to retrieve holidays in a RESTful manner.

List of endpoints:

• GET /v1/holidays/{countryCode}/upcoming

• GET /v1/holidays/{countryCode}/search/date/{holidayDate}

• GET /v1/holidays/{countryCode}/search/year/{year}

• GET /v1/holidays/search/date/{holidayDate}

Example of response:

[
  {
    "date": "2025-06-19",
    "name": "Juneteenth National Independence Day",
    "localName": "Juneteenth National Independence Day",
    "nationwide": true,
    "country": {
      "name": "United States of America",
      "localName": "United States",
      "alpha2Code": "US",
      "alpha3Code": "USA",
      "numericCode": "840"
    },
    "subdivisions": [],
    "types": [
      "Public"
    ]
  },
  {
    "date": "2025-07-04",
    "name": "Independence Day",
    "localName": "Independence Day",
    "nationwide": true,
    "country": {
      "name": "United States of America",
      "localName": "United States",
      "alpha2Code": "US",
      "alpha3Code": "USA",
      "numericCode": "840"
    },
    "subdivisions": [],
    "types": [
      "Public"
    ]
  }
]

To be able to use their API you will need to generate API key on their dashboard and subscribe for product with free trial (risk-free 3-day trial, then $110 per year or $12 per month).

Link to their API reference: https://api.finturest.com/docs/#tag/holiday