daytime (n.)

Old English dæg "period during which the sun is above the horizon," also "lifetime, definite time of existence," from Proto-Germanic *dages- "day" (source also of Old Saxon, Middle Dutch, Dutch dag, Old Frisian di, dei, Old High German tag, German Tag, Old Norse dagr, Gothic dags), according to Watkins, from PIE root *agh- "a day." He adds that the Germanic initial d- is "of obscure origin." But Boutkan says it is from PIE root *dhegh- "to burn" (see fever). Not considered to be related to Latin dies (which is from PIE root *dyeu- "to shine").

Meaning originally, in English, "the daylight hours;" it expanded to mean "the 24-hour period" in late Anglo-Saxon times. The day formerly began at sunset, hence Old English Wodnesniht was what we would call "Tuesday night." Names of the weekdays were not regularly capitalized in English until 17c.

From late 12c. as "a time period as distinguished from other time periods." From day to day was in late Old English; day-by-day "daily" is from late 14c.; all day "all the time" is from late 14c. Day off "day away from work" is attested from 1883; day-tripper first recorded 1897. The days in nowadays, etc. is a relic of the Old English and Middle English use of the adverbial genitive.

All in a day's work "something unusual taken as routine" is by 1820. The nostalgic those were the days is attested by 1907. That'll be the day, expressing mild doubt following some boast or claim, is by 1941. To call it a day "stop working" is by 1919; earlier call it a half-day (1838). One of these days "at some day in the near future" is from late 15c. One of those days "a day of misfortune" is by 1936.

Old English tima "temporal duration, limited space of time," from Proto-Germanic *timon- "time" (source also of Old Norse timi "time, proper time," Swedish timme "an hour"), reconstructed to be from PIE *di-mon-, suffixed form of root *da- "to divide."

The abstract sense of "time as an indefinite continuous duration" is recorded from late 14c. Personified as an aged bald man (but with a forelock) carrying a scythe and an hour-glass.

In English, a single word encompasses time as "extent" and "point" (French temps/fois, German zeit/mal) as well as "hour" (as in what time is it?; compare French heure, German Uhr).

It is attested from mid-14c. as "one of a number of repeated instances" (how many times?). Extended senses such as "occasion," "the right time," "leisure," or times (v.) "multiplied by" developed in Old and Middle English, probably as a natural outgrowth of such phrases as "He commends her a hundred times to God" (Old French La comande a Deu cent foiz).

to have a good time ( = a time of enjoyment) was common in Eng. from c 1520 to c 1688; it was app. retained in America, whence readopted in Britain in 19th c. [OED, 1989]

Time of day was a popular 17c. salutation ("Good time of day vnto your Royall Grace," "Richard III," I.iii.18), hence give (one) the time of day "greet socially" (1590s; earlier give good day, mid-14c.). It is preserved in negation, as what is withheld or denied in disdain or as a snub.

As "a period considered with reference to prevailing conditions," late 15c. [Men say comynly that after that the tyme goth, so must folke go]. Also in Hamlet's "The time is out of joint," etc. The times "the current age" is attested by 1590s. Times as the name of a newspaper dates from 1788. To be behind the times "old-fashioned" is from 1831; to be ahead of (one's) time is by 1837.

Time warp is attested by 1954; time-traveling in the science fiction sense is by 1895 in H.G. Wells' "The Time Machine."

Time after time "repeatedly" is by 1630s; time and again "repeatedly" is by 1864. From time to time "at intervals" is late 14c.

As the signal for the end of service in a public house, 1912, hence "closing time" in a general sense. The meaning "duration of a sentence of imprisonment is by 1837; to do time "serve a prison sentence" is by 1865. 

To be in time "not too late" is by late 15c. Adverbial on time "punctually" is by 1821. To be on time "punctual" (adj.) is by 1854 in railroading. To have no time for "lack respect or admiration for" is by 1911.

About time, ironically for "long past due time," is recorded from 1920. Next time "next occasion" is late 14c. Time off (n.) "a break from one's occupation" is by 1930.