I learned that one can transform a unix time stamp into a date by using date filter from this post:
AngularJS. Convert tag value (Unix time to human-readable time)

But I can not convert mine with it...

<td>{{contract.start_date_unix | date:'MM-dd-yyyy'}}</td>

inside the contract.start_date_unix, its valued at 1406779200

I checked it with a checker that it shows exactly what I want:
Thu, 31 Jul 2014 04:00:00 GMT (but of course, the format I want is MM-dd-yyyy, the date is correct and that's what I try to prove here)

But when I do the date filter above, it will only show 01-17-1970 or 01-16-1970...

What could be the issue cause this?