A dictionary of Confusable Phrases: More Than 10,000 Idioms and Collocations

night watch • watch night
night watch —
1
. a watch or guard kept during the night: I
used to watch them [sharks] during the night watch, as their
fins, above water, skimmed along, leaving a trail of light
behind them. 2. (also: night watchman) a man employed to
guard a building, block of offices, etc. at night: At a corner
two night watch in shoulder capes, their hands upon their
staffholsters, loom tall.
watch night—
1
. a service held on New Year’s eve, lasting
until midnight: Robert Morris, banker and merchant, attends
the Watch-Night and proceeds from here to contact friends.
2. the night upon which a New Year’s eve service is held: A
Methodist, she always goes to their chapel on New Year’s
eve — or the “Watch Night,” as they call it. 3. (West Africa) =
night watch 2: I engaged what in the Cameroons is known as
Watchnight. There were two reasons for engaging a night
watchman: the first … to wake me up.
nine-day wonder • ninety-day wonder
nine-day wonder —(also: nine days wonder) said of smth. that
causes great excitement for a few days but is likely to have
been soon forgotten: She also predicted the scandal over her
liaison with the former prime minister was a “nine-day won-
der” which would soon blow over. Cf.: one-hit wonder — said
of a group or singer that has only one hit record before returning
to obscurity: Classing Ms Shapiro as a one-hit wonder is a bit
unfair. She was an entirely unintentional pop star, having
already had a pretty healthy career in jazz.
ninety-day wonder —(also: ninety days wonder) 
1
. (U.S. Army)
a graduate of the ninety-day officer training courses: I learned
a lot from them. They were generous in their patience with a
ninety-day wonder, second lieutenant. 2. (U.S. coll.) an inex-
perienced or temporary employee: Even a ninety-day wonder
could discern the facts in this matter. 3. = nine-day wonder:
Published by Dell, with Farmer on the back cover, the book
was a ninety-day wonder.