Possibly remove double function call.

Curious to see if the double function call at the outset costs us dearly.

Removing the double function call at the outset is

Note that, we can never be as fast as a date formatter that does not localize. We need to keep track of `this`, so we need to call our functions using `call`, we can't call them directly. The only thing we can try to do to improve performance is use a switch statement.