# Generation by Birth Year Calculator

> Classifies a birth year into its named generation using the Pew Research Center birth-year boundaries (Silent 1928–1945, Baby Boomers 1946–1964, Generation X 1965–1980, Millennials 1981–1996, Generation Z 1997–2012), extended with the Lost and Greatest generations and McCrindle's Generation Alpha and Beta, and reports the age reached in a reference year and the position within the generation.

- Calculator id: `generation-by-birth-year` · Category: Everyday Life (`everyday`) · Tool name: `classify_generation_by_birth_year`
- Canonical page: https://tttkmbb.com/everyday/generation-by-birth-year · This document: https://tttkmbb.com/everyday/generation-by-birth-year.md · JSON definition: https://tttkmbb.com/everyday/generation-by-birth-year.json

## Purpose

Classifies a birth year into its named generation using the Pew Research Center birth-year boundaries (Silent 1928–1945, Baby Boomers 1946–1964, Generation X 1965–1980, Millennials 1981–1996, Generation Z 1997–2012), extended with the Lost and Greatest generations and McCrindle's Generation Alpha and Beta, and reports the age reached in a reference year and the position within the generation.

**Use when:** You need the named generation for a birth year, its year range and neighbours, whether the person is early, mid or late in the cohort, or how old that generation is in a given year.

**Do not use when:** You need an exact age in years, months and days (use age) or a zodiac sign (use zodiac); generation boundaries are research conventions that differ by a few years between sources, so do not treat them as official.

## Input

| Parameter | Type | Unit | Required | Description |
| --- | --- | --- | --- | --- |
| `birth_year` | integer |  | required | Year of birth, 1883–2039. (min 1883, max 2039) |
| `reference_date` | date |  | optional, default "today" | Date whose year is used for the age; defaults to the current UTC date. |

## Output

| Field | Type | Unit | Description |
| --- | --- | --- | --- |
| `generation` | string |  | Name of the generation. |
| `generation_years` | string |  | First–last birth year of the generation, e.g. 1981–1996. |
| `age_in_reference_year` | integer | years | Year of reference_date − birth_year (the age reached during that year; negative if not yet born). |
| `position_in_generation` | string |  | Early, Mid or Late (thirds of the generation's span), with a cusp note in the first or last two years. |
| `neighbouring_generations` | string |  | The generations immediately before and after, with their years. |
| `generation_age_range` | string |  | Youngest–oldest age of the whole generation in the reference year. |
| `source_note` | string |  | Whose boundaries define this generation. |

## Formula

`generation = range containing birth_year: Lost 1883–1900, Greatest 1901–1927, Silent 1928–1945, Baby Boomers 1946–1964, Generation X 1965–1980, Millennials 1981–1996, Generation Z 1997–2012, Generation Alpha 2013–2024, Generation Beta 2025–2039; age_in_reference_year = year(reference_date) − birth_year; position: f = (birth_year − first_year + 0.5) / span → Early (f < 1/3), Mid, Late (f ≥ 2/3)`

Silent through Generation Z use the Pew Research Center boundaries (Generation Z end year 2012); Lost and Greatest follow the Wikipedia 'Generation' overview; Generation Alpha is started in 2013 so that the timeline has no gap after Pew's Generation Z (McCrindle, who coined the name, uses 2010–2024) and Generation Beta 2025–2039 follows McCrindle. People born within a year or two of a boundary are commonly described as being on the cusp.

## Data Sources

- Pew Research Center (2019) Defining generations: Where Millennials end and Generation Z begins — https://www.pewresearch.org/short-reads/2019/01/17/where-millennials-end-and-generation-z-begins/ (reference, retrieved 2026-09-24)
- McCrindle – Understanding Generation Alpha (Generation Alpha 2010–2024, Generation Beta 2025–2039) — https://mccrindle.com.au/article/topic/generation-alpha/generation-alpha-defined/ (reference, retrieved 2026-09-24)
- Generation – named Western generations and their birth-year ranges (Wikipedia) — https://en.wikipedia.org/wiki/Generation (reference, retrieved 2026-09-24)

Data freshness: `daily` (max_age_seconds 86400). Depends on the current date unless the date is supplied.

## API

- `GET https://tttkmbb.com/api/v1/calculate/generation-by-birth-year?birth_year=…`
- `POST https://tttkmbb.com/api/v1/calculate/generation-by-birth-year` with JSON body `{"inputs": {…}}`
- Response: unified envelope (`success`, `request`, `result.values`, `result.units`, `sources`, `freshness`, `timestamp`, `next_actions`, `links`); see https://tttkmbb.com/docs/response-format.md
- Schema: https://tttkmbb.com/api/v1/calculators/generation-by-birth-year · OpenAPI operationId `classify_generation_by_birth_year` in https://tttkmbb.com/openapi.json
- Authentication: none. Rate limit: fair use, see https://tttkmbb.com/docs/rate-limits.md.

## MCP

- Server: `https://tttkmbb.com/mcp` (Streamable HTTP, JSON-RPC 2.0, no auth)
- Tool:  `run_calculator` with `{"calculator_id": "generation-by-birth-year", "inputs": {…}}`

## Example

- Born 1990, reference year 2026: inputs `{"birth_year":1990,"reference_date":"2026-09-24"}` → `{"generation":"Millennials","generation_years":"1981–1996","age_in_reference_year":36,"position_in_generation":"Mid","neighbouring_generations":"Preceded by Generation X (1965–1980); followed by Generation Z (1997–2012)","generation_age_range":"30–45"}`
- Born 2005, reference year 2026: inputs `{"birth_year":2005,"reference_date":"2026-09-24"}` → `{"generation":"Generation Z","generation_years":"1997–2012","age_in_reference_year":21,"position_in_generation":"Mid","generation_age_range":"14–29"}`

```
GET https://tttkmbb.com/api/v1/calculate/generation-by-birth-year?birth_year=1990&reference_date=2026-09-24
```

## Limitations

You need an exact age in years, months and days (use age) or a zodiac sign (use zodiac); generation boundaries are research conventions that differ by a few years between sources, so do not treat them as official. Silent through Generation Z use the Pew Research Center boundaries (Generation Z end year 2012); Lost and Greatest follow the Wikipedia 'Generation' overview; Generation Alpha is started in 2013 so that the timeline has no gap after Pew's Generation Z (McCrindle, who coined the name, uses 2010–2024) and Generation Beta 2025–2039 follows McCrindle. People born within a year or two of a boundary are commonly described as being on the cusp. All values are computed from the formula above; no measurement or live data is involved.

## FAQ

**Why do other sources give different years?**

There is no official standard. Pew's boundaries are the most cited in the US press; McCrindle uses uniform 15-year spans (e.g. Generation Z 1995–2009), and the US Census Bureau only defines the Baby Boom (1946–1964).

**What about Xennials or Zillennials?**

They are informal micro-generations on the cusps (roughly 1977–1983 and 1993–1998). This tool flags the first and last two years of each generation as cusp years instead.

## Related

- [Age Calculator](https://tttkmbb.com/everyday/age.md) — Exact age in years, months and days.
- [Zodiac Sign Calculator](https://tttkmbb.com/everyday/zodiac.md) — Western and Chinese zodiac signs for a birth date.