What is the meaning of "redeeming the time" in Ephesians 5:16?

from the old testament

• In Psalm 39:4, David makes this request of God: “‘O Lord, make me know my end and what is the measure of my days; let me know how fleeting I am!” In today’s world, people seem to forget how fleeting life is, so they live in the present and plan the future as if it were certain. But David knew that awareness of our short time on earth can help us be better stewards of it.
• In Psalm 90:12, Moses expresses a similar plea: “So teach us to number our days that we may get a heart of wisdom.” Moses was no doubt aware that people tend to squander unlimited resources. His plea to the Lord to make us aware of our mortality is so we use our time wisely.
• Proverbs 27:1 cautions against depending on an uncertain future: “Do not boast about tomorrow, for you do not know what a day may bring.” Our life is in God’s hands. If God wills it, then tomorrow will come—but it’s not certain. That’s why we should “walk circumspectly,” as Ephesians 5:15 advises (KJV).

from the new testament

• In Ephesians 5:15–16, Paul writes to Christians in Ephesus, “See then that you walk circumspectly, not as fools but as wise, redeeming the time, because the days are evil” (NKJV). Other translations say, "making the most of your time" (NASB) or "making the most of every opportunity" (NIV). The previous chapter records Paul’s exhortation for the Ephesian believers to “put off” their former corrupt life of darkness and to live as children of light (4:22). Considered in that context, Paul is advising them to make the best use of their limited time by living for the Lord.
• Colossians 4:5–6 reinforces the message of Ephesians 5:15–16, but with a slightly different focus: “Walk in wisdom toward outsiders, making the best use of the time. Let your speech always be gracious, seasoned with salt, so that you may know how you ought to answer each person.” Like Ephesians 5:16, this verse focuses on time but in the context of using it to bring others to Christ. We have just this life for the Lord to use us to make an eternal difference in others’ lives.
• James 4:13–15 also reminds us of the brevity of life: “Come now, you who say, ‘Today or tomorrow we will go into such and such a town and spend a year there and trade and make a profit’—yet you do not know what tomorrow will bring. What is your life? For you are a mist that appears for a little time and then vanishes. Instead you ought to say, ‘If the Lord wills, we will live and do this or that.’” The example James uses is of someone whose life is so focused on money that he doesn’t consider the uncertainty of tomorrow. But the wise person knows we are not promised tomorrow and that our life is in God’s hands. We can always get more money, but we can’t get more time on earth. To really make a difference, we should live for the Lord of Glory.

implications for today

“Carpe Diem” is a Latin phrase written in the Odes of Horace, a third-century B.C. Roman poem. It translates into English as “seize the day” and denotes a life of selfish, hedonistic pleasure-seeking—grabbing the gusto in contemporary terms. Most people know it, and many live by it. Christians should “seize the day,” too, but our view of that is drastically different from the norm. We are already citizens of heaven, and our life on earth should reflect that (Philippians 3:20–21). Time is a limited resource, and we must “lay up for [ourselves] treasures in heaven,” rather than pursuing empty pleasures on earth (Matthew 6:20). We do this by living for Christ. That means furthering His kingdom on earth by telling others about Him and the eternity that He has promised, a treasure infinitely more valuable than any short-term pleasures here. Solomon, the wisest man who ever lived (besides Jesus, but He is God), pursued most of the pleasures of life. But near the close of his life, he concluded, “The end of the matter; all has been heard. Fear God and keep his commandments, for this is the whole duty of man” (Ecclesiastes 12:13). Believers do well to heed that wisdom. The Bible’s emphasis on the brevity of life reminds us to live it purposefully, serving God.