dates.js

function date(year, monthNumber, day) {
  // new Date() takes a monthIndex:
  //    Integer value representing the month,
  //    beginning with 0 for January to 11 for December.
  // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/Date

  // This is a wrapper so you don't need to always subtract one

  return new Date(year, monthNumber-1, day)
}

const release_1_0 = date(2001, 1, 15);
const release_2_0 = date(2001, 3, 15);
const release_3_0 = date(2001, 9, 15);
const release_4_0 = date(2002, 6, 15);
const release_5_0 = date(2007, 1, 15);
const release_6_0 = date(2008, 2, 13);
const release_7_0 = date(2011, 1, 5);
const release_7_41 = date(2015, 10, 21);

// Generally, for D8.6+, x.y is in security support until x.y+2 is out:
// "Security fixes are provided until the following minor release, approximately
// six additional months (so each minor receives security coverage for one year
// in total and two minors receive security coverage at a time)."

// The first release to officially have security coverage for one year was 8.6.x.
// 8.5.x has unofficial extended security coverage for several SAs, but did not receive
// a backport of a Symfony issue.
// 8.4.x and earlier were strictly 7 months (six months full support plus one month
// where we would not disclose vulnerabilities in the branch without a backport).
// https://www.drupal.org/core/release-cycle-overview#comment-13702396

const release_8_0 = date(2015, 11, 19);
const release_8_1 = date(2016, 4, 20);
const release_8_2 = date(2016, 10, 5);
const release_8_3 = date(2017, 4, 5);
const release_8_4 = date(2017, 10, 4);
const release_8_5 = date(2018, 3, 3);
const release_8_6 = date(2018, 9, 5);
const release_8_7 = date(2019, 5, 1);
const release_8_8 = date(2019, 12, 4);
const release_8_9 = date(2020, 6, 3);
const release_9_0 = date(2020, 6, 3);
const release_9_1 = date(2020, 12, 2);
const release_9_2 = date(2021, 6, 16);
const release_9_3 = date(2021, 12, 8);
const release_9_4 = date(2022, 6, 15);
const release_9_5 = date(2022, 12, 15);
const release_10_0 = date(2022, 12, 15);
const release_10_1 = date(2023, 06, 21);
const release_10_2 = date(2023, 12, 13);

const eol_6 = date(2016, 2, 24);
const eol_7 = date(2025, 1, 5);

// 8.0-8.5: eol = release + 7 months
const eol_8_0 = date(2016, 6, 19);
const eol_8_1 = date(2016, 11, 20);
const eol_8_2 = date(2017, 5, 5);
const eol_8_3 = date(2017, 11, 5);
const eol_8_4 = date(2018, 5, 4);
const eol_8_5 = date(2018, 10, 3);
const eol_8_6 = release_8_8;
const eol_8_7 = release_8_9;
const eol_8_8 = date(2020, 12, 2);
const eol_8_9 = date(2021, 11, 17); // https://www.drupal.org/project/drupal/releases/8.9.20
const eol_8 = eol_8_9;

const eol_9_0 = release_9_2;
const eol_9_1 = release_9_3;
const eol_9_2 = release_9_4;
const eol_9_3 = release_9_5;
const eol_9_4 = release_10_1;
const eol_9_5 = date(2023, 11, 1); // "due to Symfony 4 EOL" [1]
const eol_9 = eol_9_5;
const eol_10_0 = release_10_2;
const eol_10_1 = date(2024, 06, 21); // TBA
const eol_10_2 = date(2024, 12, 31); // TBA
const eol_10 = date(2025, 12, 31); // TBA

// [1]
// https://www.drupal.org/about/core/policies/core-release-cycles/schedule