period of time vs mid-September

Other hyponyms of period of time include test period, trial period, time frame, grace, grace period, hours, downtime, uptime, work time, time off, bout, hospitalization, travel time, times, time, elapsed time, continuance, duration, calendar week, week, midweek, field day, life-time, life, lifespan, lifetime, life, life, millenary, millennium, bimillenary, bimillennium, occupation, past, shelf life, puerperium, lactation, time of life, calendar day, civil day, festival, day, daylight, daytime, forenoon, morn, morning, morning time, dark, night, nighttime, night, night, night, eve, evening, hebdomad, week, fortnight, two weeks, weekend, Indian summer, Saint Martin's summer, year, school, school day, schooltime, twelvemonth, year, yr, year, semester, bimester, Olympiad, lustrum, decade, decennary, decennium, century, quadrennium, quinquennium, half-century, quarter-century, quarter, phase of the moon, day, calendar month, month, mid-January, mid-February, mid-March, mid-April, mid-May, mid-June, mid-July, mid-August, mid-October, mid-November, mid-December, time limit, term, trimester, hour, silly season, Golden Age, silver age, bronze age, iron age, great year, Platonic year, regulation time, extra time, overtime, season, time of year, canicular days, canicule, dog days, midwinter, season, season, age, long time, years, long haul, long run, drought, drouth, epoch, era, generation, prehistoric culture, prehistory, reign, run, early days, youth, dawn, evening, time, nap, sleep, lease, term of a contract, half-life, half life, lunar time period, tide, phase, stage, multistage, watch, peacetime, wartime, duty tour, enlistment, hitch, term of enlistment, tour, tour of duty, honeymoon, indiction, prohibition, prohibition era, incubation period, rainy day, noviciate, novitiate, bloom, blossom, efflorescence, flower, flush, heyday, peak, prime, running time, clotting time, air alert, question time, real time, real time, study hall, usance, window, mornight.