To the Jews of New Testament times, sundown marked the end of an old day and the beginning of a new day. The twenty-four-hour period between each sundown was divided into twelve hours of night–beginning about 6:00 p.m.-and twelve hours of daylight-beginning with dawn at about 6:00 a.m.
Thou, the “third hour of the night’ (Acts 23:23) was about 9:00 p.m., and the “third hour” of the day (Matthew 20:3) was about 9:00 a.m.
The Romans used a different system for measuring the hours of the day and night. It is not always possible to tell whether the Jewish or the Roman system is being cited in the New Testament. Thus, one modern translation of the Bible renders the “tenth hour” in John 1:39 as “10 in the mourning” (HCSB), three stick with the King James Version by rendering it “tenth hour” (ESV, NASB, NKJV), and three translate it as “four o’clock in the afternoon” (CEV, NCV, NRSV).
JOHN 11:9 – Are there not twelve hours in the day [twelve hours of daylight, niv]?