I'm trying to execute some code if the current time anywhere in the world is between 8:30 AM and 5:30 PM and is not the weekend in Mountain Standard Time. I'm loading in `moment-with-locales.min.js` and `moment-timezone-with-data.min.js`. My code looks like this:

```
var format = 'hh:mm',
    date = new Date()
    mstWeekday = moment(date, 'd', 'MST')
    time = moment(date, format),
    beforeTime = moment('08:30', format, 'MST'),
    afterTime = moment('17:30', format, 'MST');

if ( (time.isBetween(beforeTime, afterTime)) && ( (mstWeekday !== 6) || (mstWeekday !== 7) ) ) {
  // Do something
}

```

If my browser is set to MST, this seems to work. If I set it to something else, like Tokyo time, it doesn't work.