adding time in seconds to hours

Question

I want to extract the hour, minutes and seconds from the date in variable e (1:25:40). Then add to the hour in the variable d ("2019-06-29 21:25:38+00"). Expected effect:

21: 25: 38 + 5140 seconds = 22: 51: 18

var d + var w = 22: 51: 18

var d = new Date("2019-06-29 21:25:38+00");
//hour --> 21:25:38

var e = new Date("2019-06-29T 1:25:40.000+00:00");

I want '1: 25: 40' to count as 1h 25 min 40 seconds

1h ---> 3600 seconds

25 min --> 1500 seconds

40 seconds

Result: 21:25:38 + 1: 25: 40 = 22:51:18

Answer 1

You can simply do

var d = new Date("2019-06-29 21:25:38+00");
d.setSeconds(d.getSeconds() + 5140);

Answer 2

Try this: new_d = new Date(d.getTime() + 5140 * 1000)

Given var d = new Date("2019-06-29 21:25:38+00") , my output is 2019-06-29T22:51:18.000Z for new_d .

The reason that this works is because .getTime() returns a long which represents the number of milliseconds since midnight on Thursday, January 1, 1970 ( there's a fun history behind this ). You can also pass a Unix-time long into the Date() constructor to get a new time object, so if you can express your offset in terms of seconds, multiply that value by 1000, add it to your original long, and you're good to go.