Yasumi is an amazing PHP library to figure out holidays in different countries. Here is handy one-liner that get you all the holidays for a specific year and prints it out.
[code lang="shell"]php -r "require 'vendor/autoload.php'; $holidays = Yasumi\Yasumi::create('USA', 2020); foreach ($holidays as $h) { echo $h->format('Y-m-d').' - '.$h->getName() . PHP_EOL; }"[/code]
Yasumi PHP Library