bad-hair day OR bad hair-day?

[P2052 at AOL.COM]

'Okay, not a great example!  What about a comparison with "Sweet Sixteen"
party?   As in "bad hair" day,  the adjective plus noun form a unit (in which
case neither receives any real stress). thus making, " Sweet Sixteen" party,
as opposed to Sweet "eixteen party."
            PAT