How long are our days?

Psalm 90 is traditionally attributed to Moses, who lived to the age of 120. His reference to human lifespan should be understood as an optimum or typical span, not as a fixed upper limit for how long an individual may live. In this sense, the psalm addresses the general reality of human physical life rather than imposing a strict boundary.

Genesis 6:3, however, requires more carefully examination. When God speaks of time in Scripture, He sometimes leaves it undefined, and at other times He specifies an exact period, such as the 70 years of Babylonian exile or the 400 years of Israel's sojourn in Egypt.

One common interpretation of the 120 years in Genesis 6:3 is that it marks the countdown from God's decree to the execution of the flood judgment. This parallels God's decree concerning Jerusalem prior to the Babylonian exile. During that intervening period, God sent prophets to call the people to repentance. Likewise, in the days before the flood, as Noah built the ark, humanity was given a final opportunity to repent before judgment fell.

Our days are known and numbered by God (Eccl 3:1-2, 11), not by a fixed formula. Psalm 90’s “70 or 80 years” reflects the typical human lifespan, while Genesis 6:3 speaks of God’s patience, not a strict limit. 120 years and 70–80 years aren’t contradictions—one shows God’s patience before judgment, the other poetically describes potential human lifespans, neither are fixed limits.

Job 14:5 — Since his days are determined, and the number of his months is with you, and you have appointed his limits that he cannot pass

James 4:14 — 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

In Hebrew narrative, statements about time—like Genesis 6:3—are often deadlines within God’s judgment speeches, not abstract principles about human biology. If Genesis 6:3 were meant as a universal lifespan limit, the text would contradict itself within the same book (cf. Genesis 11:10–32). Likewise, figures like Jehoiada, who lived 130 years (2 Chronicles 24:15), are presented as normal facts, not violations of a rule. More recently, Jeanne Calment died on August 4, 1997 at 122 years old; God's word never returns void (Isaiah 46:9-11, 55:11). The Hebrew naturally allows “time allotted” or “period of patience,” rather than requiring a statement about lifespan. The New Testament seems to support this view of divine patience or a countdown to judgment rather than a strict lifespan cap (Matthew 24:37–39; 1 Peter 3:20). Scripture also suggests that God individually numbers our days (Job 14:5; Psalm 139:16; Acts 17:26).

By contrast, Psalm 90:10’s reference to seventy or eighty years is likely best understood as a poetic, general observation. Wisdom literature often describes patterns to highlight God’s eternal nature (vv.1–4), rather than to provide absolute measurements. Psalm 90’s reference to ‘seventy or eighty years’ may reflect a typical human lifespan in some interpretations, but it does not constitute a fixed or universal limit for everyone. Note that the text uses no commanding verbs like “shall be” or “must be,” and later prays, “Teach us to number our days” (v.12). If the number were already fixed, this prayer would appear redundant. Instead, it reflects human humility before God, who alone truly knows the span of our lives. Scripture consistently portrays life as appointed by God according to His will (Isaiah 65:20; John 21:22; Hebrews 9:27).

"How many days will we have to live?" And the answer to that is, quite simply, "For as many days as God decrees we shall live."

Consider how God decided to put to death individuals that never reached anywhere near old age (whatever time any given generation considers to be 'old age'. These days, anyone who has lived longer than a quarter of a century is - in my opinion - old, and I should know.)

Look at the case of Judah's two sons.

"Judah got a wife for Er, his firstborn, and her name was Tamar. But Er, Judah's firstborn, was wicked in the Lord's sight; so the Lord put him to death." Genesis 38:6-7 NIV

This was before he fathered any children; the record indicating that he was a young man, barely middle-aged. And then his younger brother Onan was also put to death by the Lord, for his wickedness (Gen. 38:10).

Note that they died long after the Flood, when the average life-span was then cut down to 120 years. However, the patriarch Job lived 140 years and Abraham lived 175 years. It wasn't until after the death of Joseph, aged 110 years, that the downward trend continued until 70 to 80 years was considered to be 'old', as Psalm 90:10 indicates.

Whether 120, or the more recent 70 to 80 years, those are average ages, generally speaking. Today, very few people reach 100 years. We have clearly been living in the 70 to 80 group for centuries, with mortality generally being, on average, lower than 70, especially when infant mortality ages are taken into account.

As for our days being "numbered" - well, that is known only to God who tells us time and again that our days fly away; we are like grass that withers, like flowers of the field that soon fade and die - see Psalm 73:23-24 & 49:15. And the older people get, they become more aware of that truth. The need is to learn how to count our days as living for God and pleasing him. Then we have nothing to worry about as to whether we live many years, or few.

Not so fast - Gen 6:3 and Ps 90:10 are discussing two different things, despite the similarity in language. Specifically:

Genesis 6:3 - And the LORD said, “My Spirit shall not strive with mankind forever, for he is indeed flesh; yet his days shall be one hundred and twenty years.”

This is talking about the time of probation granted to humankind before the flood came to destroy sinful humans and "everything that breathes" (Gen 6:17, 7:22). People died because of the judgement of God. In that great deluge, those that died consisted of both young and old.

Ps 90:10 - As for the days of our life, they contain seventy years, Or if due to strength, eighty years, Yet their pride is only trouble and tragedy; For it quickly passes, and we disappear.

This is talking about the natural length of human life, its transitory nature, and how short it is compared to eternal matters, especially God. That is, it is encouraging a sense of perspective (V3) - some feel very important but Moses reminds us that we live a short time and God is eternal (V2, 4) and omnipotent.

This is suggesting that we need God, are dependent on God, and should seek his "loving kindness", mercy and grace (V13-15).