I have a date in UTC in javascript, and I would like to substract some hours.

I searched online and apparently I should concat the substraction to the date like the following:

```
const diff = "-5"
const utcDate = "2017-02-22 17:28:13"
const date = new Date(utcDate + diff[0] + ' ' + diff[1])
//desired output: 2017-02-22 12:28:13

```

But I can't seem to make it work.