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JavaScript: Find whether or not the date is in daylights savings time

JavaScript Datetime: Exercise-38 with Solution

Write a JavaScript function to find whether or not the date is in daylights savings time.

Test Data :
dt = new Date();
console.log(daylights_savings(dt));
1

Sample Solution:-

HTML Code:

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>JavaScript function to find whether or not the date is in daylights savings time.</title>
</head>
<body>

</body>
</html>

JavaScript Code:

function daylights_savings(dt) 
{ 
  var dst = null;
  for (var i = 0; i < 12; ++i) 
    {
      var d = new Date(dt.getFullYear(), i, 1);
      var offset = dt.getTimezoneOffset();

      if (dst === null) 
        dst = offset;
      else if (offset < dst) 
         {
           dst = offset; 
           break;
         } 
      else if (offset > dst) 
        break;
         }
return (dt.getTimezoneOffset() == dst) | 0;
}

dt = new Date(); 
console.log(daylights_savings(dt)); 

dt = new Date(1989, 10, 1); 
console.log(daylights_savings(dt));

Sample Output:

1
1

Flowchart:

Flowchart: JavaScript- Find whether or not the date is in daylights savings time

Live Demo:

See the Pen JavaScript - Find whether or not the date is in daylights savings time-date-ex-38 by w3resource (@w3resource) on CodePen.


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Next: Write a JavaScript function to get difference to Greenwich time (GMT) in hours.

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JavaScript: Tips of the Day

Convert tabs to spaces, where each tab corresponds to count spaces

Example:

const tips_expandTabs = (str, count) => str.replace(/\t/g, ' '.repeat(count));
console.log(tips_expandTabs('\t\tw3resource', 4)); 

Output:

"        w3resource"