[javascript] How do I subtract minutes from a date in javascript?

Once you know this:

  • You can create a Date by calling the constructor with milliseconds since Jan 1, 1970.
  • The valueOf() a Date is the number of milliseconds since Jan 1, 1970
  • There are 60,000 milliseconds in a minute :-]

...it isn't so hard.

In the code below, a new Date is created by subtracting the appropriate number of milliseconds from myEndDateTime:

var MS_PER_MINUTE = 60000;
var myStartDate = new Date(myEndDateTime - durationInMinutes * MS_PER_MINUTE);