As a writer, I am asked occasionally to submit an article for publication. Attached to these requests is a deadline, usually not far off. Having a deadline helps me focus my research and writing so that I can turn out a good article in a short time.
According to 1 John 2:18, we all live under the deadline of eternity.
Dear children, this is the last hour; and as you have heard that the antichrist is coming, even now many antichrists have come. This is how we know that it is the last hour.
Let’s interpret this verse one phrase at a time.
First, dear children: John is the spiritual father of the people he is writing to. He is not a boss giving an assignment, a doomsday alarmist scaring the masses, or an end-times novelist selling books. He is, instead, a parent concerned about the wellbeing of his spiritual children. He has a parental sense of urgency about the eternal deadline under which they live.
Second, this is the last hour: First John 2:18 is the only place in the New Testament where the phrase the last hour appears. However, it is similar in meaning to the phrases the last days or the last times. According to Colin G. Kruse, “In some cases these [phrases] refer to the whole period begun by the first coming of Jesus and running through to his final parousia [i.e., second coming] (cf. Acts 2:17; Heb 1:2; 1 Pet 1:20). In other cases they refer to the last part of that period, just prior to the final parousia (cf. 2 Tim 3:1; Jas 5:3; 2 Pet 3:3; Jude 18). The last part of the period, it is said, will be marked by various difficulties and tribulations (2 Tim 3:1; 2 Peter 3:3; Jude 18).” Whatever the specific reference is to in 1 John 2:18, it is clear that we are drawing closer to our eternal deadline.
Third, as you have heard: Evidently, teaching about the end times generally and the antichrist specifically was part of John’s apostolic teaching. It is part of the warp and woof of authentic Christianity.
Fourth, the antichrist is coming, even now many antichrists have come. The antichrist is the great opponent of God, Christ, and the church who will arise at the end of the last days. Elsewhere, the New Testament refers to him as the “man of lawlessness” (2 Thessalonians 2:3), the [false] “Christ” (Matthew 24:26, Mark 13:21), and the “beast” (Revelation 13:1). But John adds that the antichrist has many forerunners, who are also “antichrists” because they deny that “Jesus is the Christ” (1 John 2:22).
Fifth, this is how we know that it is the last hour: We know we live in the last days because every advance of the gospel is met by a determined spiritual counteroffensive. As people who live under an eternal deadline, we need to keep our guard up. Nobody said that keeping our eternal deadline would be easy, only that it would be worth it.
 Colin G. Kruse, The Epistles of John (Grand Rapids, MI: Eerdmans, 2000), 98.