The New Testament uses four Greek words for “time,” kairos, hora, chronos, and aion. The two most important senses of time are kairos and hora.
Kairos is God’s appointed time and purpose for a particular event. For instance, “The time [kairos] is fulfilled, and the kingdom of God is at hand; repent, and believe in the gospel” Mk 1:15, or “Go to the feast yourselves; I am not going up to this feast, for my time [kairos] has not yet fully come” Jn 7:8. The souls in purgatory are on kairotic time, they await God’s taking them into heaven but without any measure of when it will occur. They wait patiently, and then pass into heaven. In rhetoric, kairos is also a passing instant when an opening appears which must be driven through with force to attain success.
Hora, “hour,” is used often in the Gospels. About a third of the time it simply refers to clock time. The Jewish method of calculating time divided the whole day into eight parts, four night parts (called “watches”) and four day parts (called “hours”)–the first, third, sixth and ninth hour. The first hour began at sunrise and ended around nine o’clock; the third ran to twelve noon; the sixth to three in the afternoon; and the fourth from three to sunset. Other hora references are to a crucial or decisive time, such as the times when Rabbi Yeshua is arrested, crucified, or raised from the dead; in this usage it is similar to kairotic time.
Chronos is time in the material realm, this life, measured in minutes, hours, days, weeks, months, etc. “Now the time [chronos] came for Elizabeth to be delivered, and she gave birth to a son” Lk 1:57.
An aion (eon) is ordinarily a broad sweep of time. “Whoever speaks against the Holy Spirit will not be forgiven, either in this age [aioni] or in the age to come [mellonti] Mt 12:32.
The Septuagint reveals the distinction between kairos and chronos. “For everything there is a season [kairos], and a time [chronos] for every matter under heaven” Ecc 3:1.
Scott Hahn: The Hour is Coming 1:07:24