No, if it's 8:00PM EST, it would be 6:00PM MST in Phoenix but 5:00PM PST here where I live.
Now when we go to DST, and it's 9:00PM EDT, it would be still be 6:00PM MST in Phoenix and 6:00PM PDT.
I think :-)
Phoenix at this moment in time is the same as the West Coast. (CA)