Daylight Saving Time Calendar Tool

The Global Evolution of Daylight Saving Time

Daylight Saving Time (DST) is the policy of advancing local clocks by one hour during spring and summer months to extend evening daylight and conserve energy. While championed historically as a coal-saving measure during World War I, modern energy and health research has transformed DST into a subject of global debate.

Key Regional Transition Rules

• United States & Canada: Operates under the Energy Policy Act of 2005. DST begins on the second Sunday of March and ends on the first Sunday of November. Hawaii and Arizona (except Navajo Nation) remain on Standard Time. Explore complete schedules on our DST Calendar Page and DST Start & End Dates.
• European Union & UK: Governed by EU Directive 2000/84/EC. Summer Time begins on the last Sunday of March at 01:00 UTC and ends on the last Sunday of October at 01:00 UTC. See CET to EST.
• Australia & New Zealand: Southern Hemisphere nations observe DST during their summer months. In Australia, New South Wales, Victoria, Tasmania, South Australia, and ACT advance clocks on the first Sunday of October and revert on the first Sunday of April. Queensland, Western Australia, and Northern Territory do not observe DST. Learn more at Australia Time Zones.

Nations That Have Abandoned DST

Over 130 countries worldwide do not observe seasonal clock shifts. Equatorial nations naturally experience consistent 12-hour day/night cycles year-round, rendering DST obsolete. Notable policy changes include:

• Mexico (2022): Abolished DST nationwide except for border towns aligned with US commerce. Read our Countries Without DST Guide.
• Brazil (2019): Discontinued DST to eliminate health and economic disruptions.
• Turkey (2016) & Russia (2014): Shifted permanently to year-round Standard Time or Permanent Daylight Time.

Developer Code Snippet: Detecting DST in JavaScript

Software developers can check if a given date falls within Daylight Saving Time by comparing its timezone offset against January (winter) and July (summer) offsets:

// Function to check if a Date object falls in DST for a specific target location
function isDateInDST(d, timeZone) {
  const jan = new Date(d.getFullYear(), 0, 1);
  const jul = new Date(d.getFullYear(), 6, 1);

  const getOffset = (date) => {
    const utcDate = new Date(date.toLocaleString('en-US', { timeZone: 'UTC' }));
    const tzDate = new Date(date.toLocaleString('en-US', { timeZone }));
    return tzDate.getTime() - utcDate.getTime();
  };

  const stdOffset = Math.min(getOffset(jan), getOffset(jul));
  const currentOffset = getOffset(d);

  return currentOffset > stdOffset;
}

console.log("Is New York in DST today?", isDateInDST(new Date(), "America/New_York"));

For broader timezone calculations, explore our DST Explanation Article, Business Impact of DST Guide, Global World Clock, and Developer Toolkit.