Elijah's Drought - In 1 Kings 18:1-46, Elijah prayed for a drought to cause Ahab to repent. According to James 5:17, "it rained not upon the earth by he space of three years and six months."
The Two Witnesses - According to Revelation 11:1-12, not only did their efforts to bring mankind to repentance last for three and a half years, after they were killed, their bodies did lie in the street for three and a half days, for all to see. Their resurrection, and ascension was also seen by all!
The Ministry of Jesus - To begin with, I believe Jesus was born in the Fall of 5 B.C. There are a couple of reasons for my believing that: for the year, Herod the Great died in 4 B.C. and Jesus was born about a year prior to his death (Mt. 2:13-23); as for the season, the Shepherds were not likely to be watching their flocks out in the fields in Winter (Lk. 2:8-20). Since Jesus was born in the Fall, and crucified in the Spring (Passover), that would mean His ministry to bring Israel to repentance and offer Himself as their Messiah, lasted three and a half years. Note: Passover occurred on April 25th of the year A.D. 28. And, by the way, it was on a Wednesday, which is in harmony with Jesus' statement in Matthew 12:40.
The Two Halves of the Tribulation - The Tribulation will be a call to repentance, as well (Rev. 2:5, 16, 22; 3:3, 19; 9:20-21; 16:9, 11). Daniel 9:27 says, "And he (Antichrist / Beast) shall confirm the covenant with many for one week (seven years): and in the midst of the week (three and a half years into the seven years) he shall cause the sacrifice and the oblation to cease, and for the overspreading of abominations he shall make it desolate, even until the consummation, and that determined shall be poured upon the desolate" (see Mt. 24:15; 1 Jn. 2:18; Rev. 13:1-18). We know that the "seven" refers to years, because they are described as 1260 days (Rev. 11:3; 12:6); 42 months (Rev. 11:2; 13:5); and a "time, times, and a half time" (Dan. 7:25; 12:7; Rev. 12:14).
Do you have three seconds, minutes, hours, days, months, years?
You do not know how much time you have left to trust in Jesus!
Repent and accept Him as your Lord now, while there is still time!