startOf is not using setDefault timezone

[renatoagds]

When I use setDefault to a specific timezone, startOf is not assuming that timezone and is using local timezone instead.

var localActual = moment([2016, 1, 1, 16, 0, 0]).unix();
var localStart = moment([2016, 1, 1, 16, 0, 0]).startOf('day').unix();

moment.tz.setDefault('America/Los_Angeles');

var mockedActual = moment([2016, 1, 1, 16, 0, 0]).unix();
var mockedStart = moment([2016, 1, 1, 16, 0, 0]).startOf('day').unix();

console.log(localActual === mockedActual); // false
console.log(localStart === mockedStart); // true

I already created an example in my codepen, here.

[mattjohnsonpint]

Dup #208

Thanks.