Jewish Encyclopedia, p. 591- 597

"In order to fix the beginning and ending of the Sabbath-day and festivals and to determine the precise hour for certain religious observances it becomes necessary to know the exact times of the rising and setting of the sun. According to the strict interpretation of the Mosaic law, every day begins with sunrise and ends with sunset... "

Vine’s Complete Expository Dictionary of Old and New Testament Words

“In the Hebrew mind the “DAY” began at the rising of the sun.”

Ancient Israel, p. 181 - 182

“In Israel, the day was for a long time reckoned from morning to morning… and it was in fact in the morning, with the creation of light, that the world began; the distinction of day and night, and time too, began on a morning (Gen. 1:3-5, cf. 14:16, 18). The opposite conclusion has been drawn from the refrain which punctuates the story of creation: “There was an evening and there was a morning, the first, second, etc., day;.” This phrase, however, coming after the description of each creative work (which clearly happens during the period of light), indicates rather the vacant time till the morning, the end of a day, and the beginning of the next work… The change of reckoning must therefore have taken place between the end of the monarchy and the age of Nehemiah… This would bring us to the beginning of the [Babylonian] exile…”

New Catholic Encyclopedia - Volume 11 p.1068

"Days were reckoned from morning to morning... Following the reign of King Josiah (c. 640-609), and especially after the Babylonian exile a number of significant and enduring changes occurred in the Israelite calendar showing that the Hebrews gradually adopted the Babylonian calendar of the time...the seven day week persisted despite its failure to divide evenly either the month or the year. the day however, was counted from evening to evening, after the Babylonian fashion..."

Rabbinic Essays, Page 447- 451

“In certain spheres of the population the older system continued to be in use, either exclusively or side by side with the newer system. Thus in the temple service the older system continued all through the time of the existence of the second temple, and there the day was reckoned from morning to morning…”

Supplementary Studies in the Calendars of Ancient Israel p. 1-148

“. . .the time of the transition from the reckoning of the day as beginning with morning to the reckoning of it as beginning with evening… that in the earlier calendar and in the literature which records this, the day was reckoned from the morning, presumably from sunrise, while in the later calendar and the literature pertaining thereto the day was reckoned from the evening… Elsewhere we have presented quite a mass of evidence which establishes conclusively that the earlier practice in Israel during the Biblical period was to reckon the [24 hour] day from sunrise to sunrise… That in the earliest period of Israelite sojourn in Palestine, under calendar 1, the day was reckoned from morning to morning is established by a super abundance of evidence… This in turn, together with other important considerations, would point to a time approximately about the beginning or the first half, of the third century B.C. as that of the introduction of the new system of reckoning the day.”