Someone born on March 15, 1990 is in late summer right now
On October 18, 2026, a person born on March 15, 1990 is 36.6 years old. Using United States life tables (both sexes), a 36.6-year-old can expect about 44.5 more years, so the reference lifespan is 81.0 years. With equal quarters, summer runs from age 20.0 to 40.7. This person is 80.2% of the way through it, which makes it late summer. Autumn begins on November 18, 2030, at age 40 years 8 months, which is 4 years 1 month away. Age 40.7 is the halfway point of life: the life expectancy still ahead (40.7 years) equals the years already lived.
The calculator above does the same thing for any birth date. The season wheel fills up as your life progresses, and the season map lays out ages 0 to the reference lifespan so you can see the date each season begins and ends. The default basis is the United States. You can switch to the United Kingdom, Japan, Korea (from the national statistics office, MODS), Spain, Mexico, Indonesia or the world average, pick a sex, or type your own reference lifespan. To count the days you have been alive, try the Days Lived Counter; for your age down to the day, use the Age Calculator.
When it helps to see your life as seasons
The psychologist Daniel Levinson, who built his model of adult development on the metaphor of seasons, wrote: "No season is better or more important than any other. Each has its necessary place and contributes its special character to the whole." A season gives you a short, human way to say where you are, which a plain number of years does not.
- At a birthday or New Year: see how far the wheel has turned in the past twelve months and how much of the current season is left, then plan the next year around it.
- Before a big decision such as a career change, a startup or retirement: the date and age at which the next season begins turn a vague "someday" into a concrete span, such as 4 years 1 month before autumn.
- Comparing with family: enter a parent, a partner and a child in turn and see that on the same day each of them is in a different season.
- In a class, workshop or counseling session: switch to Levinson eras to show early adulthood, middle adulthood and late adulthood with the transitions between them hatched on the bar.
How it is calculated
- Exact age: your age in whole years plus the days since your last birthday divided by the days between that birthday and the next. For March 15, 1990, the person is 36 on October 18, 2026, with 217 days since the last birthday: 36 + 217 ÷ 365 = 36.59. Someone born on February 29 counts March 1 as the birthday in non-leap years.
- Reference lifespan: exact age plus the life expectancy remaining at that age. The life table only lists ages 0, 1, 5, 10 and so on up to 100+, so values in between are found by drawing a straight line between neighboring ages. At 36.59, life expectancy is 44.45 years, between 45.93 at age 35 and 41.30 at age 40 (United States, both sexes), giving a reference lifespan of 81.0.
- Dividing into seasons: for "Equal quarters", boundary k is the age x at which a quarter of the reference lifespan at that age has passed, or x = k/4 × (x + life expectancy at x), for k = 1, 2, 3. For the United States (both sexes) this gives ages 20.0, 40.7 and 63.5. "Every 20 years" changes seasons at 20, 40 and 60, and "Levinson eras" at 22, 45 and 65. In every method winter lasts until today's reference lifespan.
- Position inside the season: the share of the season already passed is shown as a percentage and cut into thirds: early, mid and late.
- When the next season starts: the first day on which your exact age reaches the next boundary. The boundary ages never move as you get older, so the date stays fixed. The only thing that grows from year to year is the reference lifespan at which winter ends.
Reference lifespan and season at each birthday
These rows use the United States life table (both sexes) with equal quarters. As you get older the remaining life expectancy shrinks, but you are also a survivor of every earlier age, so age plus remaining life expectancy actually goes up. That is why the reference lifespan, where winter ends, creeps up with age.
| Birthday age | Life expectancy left | Reference lifespan | Season on that birthday |
|---|---|---|---|
| 0 | 79.30 years | 79.30 | Early spring 0.0% |
| 10 | 69.83 years | 79.83 | Mid-spring 49.9% |
| 20 | 60.02 years | 80.02 | Late spring 99.9% |
| 30 | 50.58 years | 80.58 | Midsummer 48.3% |
| 40 | 41.30 years | 81.30 | Late summer 96.7% |
| 50 | 32.25 years | 82.25 | Mid-autumn 40.8% |
| 60 | 23.88 years | 83.88 | Late autumn 84.6% |
| 70 | 16.27 years | 86.27 | Early winter 28.5% |
| 80 | 9.61 years | 89.61 | Midwinter 63.1% |
| 90 | 4.69 years | 94.69 | Late winter 84.9% |
Life expectancy is an average that assumes today's death rates stay the same at every age. In the United States table, life expectancy at birth is 79.30 years for both sexes: 76.86 for males and 81.85 for females. At age 60 it is 22.36 more years for males and 25.32 for females.
Three ways to divide the seasons
Here is the same person (born March 15, 1990, reference lifespan 81.0) under each method.
| Method | Spring | Summer | Autumn | Winter | October 18, 2026 |
|---|---|---|---|---|---|
| Equal quarters | 0–20.0 | 20.0–40.7 | 40.7–63.5 | 63.5–81.0 | Late summer 80.2% |
| Every 20 years | 0–20 | 20–40 | 40–60 | 60–81.0 | Late summer 82.9% |
| Levinson eras | 0–22 | 22–45 | 45–65 | 65–81.0 | Midsummer 63.4% |
- Equal quarters puts each boundary where life is a quarter, a half and three quarters over, measured against the reference lifespan at that age. Spring ends when the life expectancy remaining is three times the years lived; summer ends at the halfway point, where the two are equal; autumn ends when the remaining life expectancy is a third of the years lived. The seasons are therefore slightly unequal (20.0, 20.7, 22.8 and 17.6 years for this person), and country and sex move the boundaries.
- Every 20 years has fixed boundaries at 20, 40 and 60, which are easy to remember. The cost is uneven seasons: the longer the reference lifespan, the longer winter becomes.
- Levinson eras follow the work of Daniel J. Levinson of the Department of Psychiatry, Yale University School of Medicine, who based his scheme on "the 40 men interviewed in my first study (1978) and the 45 women interviewed in my current study" (American Psychologist, 1986). He placed the first era from "conception to roughly age 22", early adulthood at "about age 17 to 45" and middle adulthood at "about age 40 to 65"; late adulthood "starts at about age 60". Eras overlap: "A new era begins as the previous one is approaching its end," and each transition "generally lasts about five years". The calculator uses the end of each era (22, 45 and 65) as the season boundary and hatches the overlaps at 17–22, 40–45 and 60–65.
Early, mid and late
Each season is cut into three equal thirds, and the name of the third is shown on top of the season name. The same cut applies to all three methods.
| Part of the season | Share of the season passed | Example name | In the example above |
|---|---|---|---|
| Early | 0–33.3% | Early summer | Not yet |
| Mid | 33.3–66.7% | Midsummer | Not yet |
| Late | 66.7–100% | Late summer | 80.2% puts the person here |
Five people on October 18, 2026
The basis is the United States, both sexes. The percentage is the share of the current season already passed. "Transition" means the person falls inside an overlap of Levinson's eras (17–22, 40–45 or 60–65). The same person can land in a different season depending on the method.
| Date of birth | Age | Reference lifespan | Equal quarters | Every 20 years | Levinson eras |
|---|---|---|---|---|---|
| May 5, 2008 | 18 | 80.0 | Late spring 92.2% | Late spring 92.2% | Late spring 83.8%, transition |
| March 15, 1996 | 30 | 80.6 | Midsummer 51.2% | Midsummer 52.9% | Midsummer 37.3% |
| November 2, 1984 | 41 | 81.5 | Early autumn 5.6% | Early autumn 9.7% | Late summer 86.7%, transition |
| July 20, 1970 | 56 | 83.2 | Late autumn 68.2% | Late autumn 81.2% | Mid-autumn 56.2% |
| February 10, 1955 | 71 | 86.8 | Midwinter 35.1% | Midwinter 43.6% | Early winter 30.7% |
The person born on November 2, 1984 shows how much the method matters. With equal quarters and with every 20 years, they are already in early autumn (5.6% and 9.7%): the next season, winter, starts on May 3, 2048 and on November 2, 2044. With Levinson eras, they are still in late summer (86.7%), inside the Midlife Transition, and autumn begins on November 2, 2029, the day they turn 45.
How sex and country change the boundary ages
With equal quarters, a longer life expectancy pushes every boundary later. In the United States table (UN World Population Prospects 2024), the halfway point where autumn starts is age 40.7 for both sexes, 39.6 for males and 41.7 for females, a gap of 2.1 years.
| United States | Life expectancy at birth | Summer starts | Autumn starts (halfway) | Winter starts |
|---|---|---|---|---|
| Both sexes | 79.3 years | age 20.0 | age 40.7 | age 63.5 |
| Male | 76.9 years | age 19.4 | age 39.6 | age 62.2 |
| Female | 81.9 years | age 20.6 | age 41.7 | age 64.6 |
Country makes a bigger difference. The table below is for both sexes.
| Basis | Life expectancy at birth | Summer starts | Autumn starts (halfway) | Winter starts |
|---|---|---|---|---|
| United States | 79.3 years | age 20.0 | age 40.7 | age 63.5 |
| United Kingdom | 81.3 years | age 20.4 | age 41.2 | age 63.7 |
| Japan | 84.7 years | age 21.3 | age 42.8 | age 65.7 |
| Korea (MODS 2024) | 83.7 years | age 21.0 | age 42.4 | age 65.0 |
| Spain | 83.7 years | age 21.0 | age 42.2 | age 64.9 |
| Mexico | 75.1 years | age 19.1 | age 39.1 | age 61.3 |
| Indonesia | 71.2 years | age 18.3 | age 37.2 | age 58.1 |
| World average | 73.2 years | age 19.2 | age 39.1 | age 61.2 |
Every row except Korea comes from the UN World Population Prospects 2024 (2023 estimates). Korea uses the 2024 life table of Korea's statistics office (MODS), which differs slightly from the UN's own Korean figures.
Common mistakes
- Using life expectancy at birth for every age: for a 70-year-old, 79.30 would suggest only 9.3 years are left. But life expectancy at 70 is 16.27 more years, so the reference lifespan is 86.27. This calculator always uses the remaining life expectancy at your current age.
- Reading life expectancy as a promise: it is an average that assumes current death rates stay the same. The reference lifespan is a yardstick for dividing the seasons, not a forecast of how long anyone will live.
- Dividing today's reference lifespan into four equal parts: the reference lifespan grows a little every year, so boundaries set from today's value drift later and the season would not change on the date you were told. This calculator fixes each boundary age instead, so the date holds.
- Taking Levinson's ages as exact: he wrote "about" and "roughly" for every boundary. The hatched transitions mean that many people rebuild their life structure around those ages, not that everyone does.
- Subtracting birth years: 2026 minus a birth year can be a year too high if the birthday has not happened yet. The calculator uses your exact birth date.
Limits of this calculator
- The seasons are a metaphor for reflecting on a life. Health, family history and lifestyle are not taken into account.
- Life tables list ages 0, 1, 5, 10 and so on, so in-between ages use straight-line interpolation. The result can differ from a full single-year table by about 0.1 year. Ages of 100 and over use the single "100+" value.
- Korea uses the 2024 table and the other countries use 2023 estimates. Values will change when new tables are published.
- A custom reference lifespan must be a whole number from 70 to 120. If your age passes it, the result shows winter at 100%.
- Birth dates from January 1, 1900 up to today are accepted. Nothing is saved on the page or on your device, so use "Copy result" to keep a record.
Basis The United States figures come from the UN World Population Prospects 2024 (2023 estimates), and the Korea figures from the MODS 2024 life table. Both were checked on October 18, 2026, and every example on this page was calculated on that date.
Sources
- 01UN DESA: World Population Prospects 2024Abridged life tables, 2023 estimates, medium variant, both sexes and by sex
- 02Levinson, D. J. (1986). A conception of adult developmentAmerican Psychologist, 41(1), 3–13
- 03MODS (Statistics Korea): 2024 life tablePublished December 3, 2025; used for the Korea basis
Frequently asked questions
How does the Seasons of Life Calculator decide the seasons?
It adds the remaining life expectancy at your current age to that age to get a reference lifespan, then divides life into four seasons. The default basis is the United States life table (UN World Population Prospects 2024). Someone born on March 15, 1990 is 36.6 on October 18, 2026 with 44.5 years of life expectancy left, so the reference lifespan is 81.0 and summer (20.0 to 40.7) is 80.2% over: late summer.
Why not just use life expectancy at birth, 79.3 years?
That figure is the average for a newborn. People who have already reached an age have, on average, more years ahead of them than a newborn's average implies. At 60 the reference lifespan is 60 + 23.88 = 83.88, and at 80 it is 89.61. Using life expectancy at birth for everyone makes winter look shorter the older you are.
What season is someone born in 1990 in?
It depends on birthday and basis. Someone born on March 15, 1990 is in late summer on October 18, 2026 with the United States basis (80.2% of summer passed). Autumn begins on November 18, 2030, at age 40 years 8 months. Choosing male moves the boundaries earlier, so autumn comes sooner; choosing female pushes them later.
What is the difference between equal quarters, every 20 years and Levinson eras?
With equal quarters, boundaries sit where a quarter, a half and three quarters of the reference lifespan at that age have passed (ages 20.0, 40.7 and 63.5 for the United States), and they never move. Every 20 years changes seasons at 20, 40 and 60. Levinson eras change them at 22, 45 and 65. Winter always lasts until today's reference lifespan. Someone born on November 2, 1984 is in early autumn with the first two methods, but in late summer, inside the Midlife Transition, with Levinson eras.
What are Levinson's transitions?
Daniel Levinson (1986) described pre-adulthood (to roughly age 22), early adulthood (about 17 to 45), middle adulthood (about 40 to 65) and late adulthood (from about 60). Neighboring eras overlap, and each transition generally lasts about five years: 17 to 22, 40 to 45 and 60 to 65. The calculator hatches these ranges on the season map.
How are early, mid and late summer decided?
By how much of the current season has passed. Under 33.3% is early, under 66.7% is mid and the rest is late. A person who is 80.2% through summer is in late summer.
How much does sex change the result?
In the United States table, the halfway point where autumn starts (remaining life expectancy equals years lived) is age 39.6 for males, 40.7 for both sexes and 41.7 for females, a gap of 2.1 years between female and male. Summer starts at 19.4 for males and 20.6 for females, and winter at 62.2 and 64.6. If you pick no sex, the both-sexes figures are used.
Can I enter my own reference lifespan?
Yes. Choose Custom under life expectancy basis and enter a whole number from 70 to 120. A custom value does not change with your age, so the season boundaries stay fixed. If your age passes it, the result shows winter at 100% and tells you how far past it you are.