this.get('moment').moment().utc does not work properly

Hello,
I have an issue with utc.
Following code works:
```javascript
moment.utc('01.01.1998', 'DD.MM.YYYY'); //returns the expected moment object(1998-01-01)
```
and following does not work:
```javascript
this.get('moment').moment().utc('01.01.1998','DD.MM.YYYY'); //returns the current date
```

What's the difference between using the service injected via
```javascript
moment: Ember.inject.service()
```
and using moment directly?

What's my mistake?
Thx