bad-hair day OR bad hair-day?

[P2052 at AOL.COM]

Probably not!  The original reference was to a day (any day) during which the
hair was not manageable.  And, since there is no such phenomenon as "hair
day," the adjective "bad," is modifying "hair" (at least in the original
description), not "day."
Referring to a "bad hair-day," is tantamount to referring to the phrase from
the children's tv program as, "Howdy Doody-Time."
                                    P-A-T