Formating date issue

I am using: =Format(CDate(First(Fields!startdate.Value,"DataSet4")),"MM/dd/yyyy")

to try to format "06/10/2015 00:00:00:000 -04:00"

But I am not having any luck. Any idea?
Also I will need to for mat the UTC on another field. Not sure how to do that too

Based on my reading of this page, it looks like you should get rid of the offset before formatting like shown below rather than use CDate.

=Format(First(Fields!startdate.Value.DateTime,"DataSet4"),"MM/dd/yyyy")

Disclaimer: I haven't tried it, so...

This just gives me an error