Nighttime rhymes with:
parttime, airtime, alltime, anytime, bedtime, centime, christmastime, daytime, dinnertime, downtime, everytime, flextime, fulltime, funtime, halftime, lifetime, longtime, lunchtime, maritime, mealtime, meantime, movietime, noontime, overtime, parttime, pastime, peacetime, primetime, quicktime, ragtime, schooltime, showtime, sometime, springtime, summertime, wartime, wintertime
Nighttime sounds like:
nakatani, naughton, negation, negotiation, nekton, neustine, nicodemo, nicotine