📅Date & Time

Daylight Saving Patterns

When and how clocks change for summer/winter time.

Explanation

DST shifts clocks forward in spring and back in autumn, usually by one hour, to extend daylight.

Examples

Spring Forward

Output

+1 hour (Spring)

Fall Back

Output

-1 hour (Autumn)

Code Examples

JavaScript

function isDST(date) {
  const jan = new Date(date.getFullYear(), 0, 1).getTimezoneOffset();
  const jul = new Date(date.getFullYear(), 6, 1).getTimezoneOffset();
  return date.getTimezoneOffset() < Math.max(jan, jul);
}

💡 Tips

Not all countries use DST
Shift usually happens at 02:00 local time
Southern hemisphere seasons are reversed

⚠️ Common Pitfalls

A 23-hour or 25-hour day once a year
Ambiguous hour when "falling back" (01:00 happens twice)