In my production/heroku app, the code below returns a number of hours that is 7 hours more than the number of hours returned by the code below when it is run in my development/local application. Why is this?

```
var startDate = moment.tz("2000-01-01", "America/Edmonton").startOf('day');
var endDate   = moment.tz("America/Edmonton");

hourly_count = parseInt(endDate.diff( startDate, 'hours' ) + 1 );

```