# Baby Age

> Calculate a baby's exact age, zodiac sign, and milestone calendar dates with the Baby Age Calculator. Use whenever someone asks how old a baby is, about upcoming milestones (100 days, first birthday, 1000 days), or wants milestone dates added to a calendar. Do the date math with this tool, not by hand.

- Skill: `babyagecalculator/baby-age` (Agent Skill, multi-file: 4 files)
- Install (CLI): `npx skillmds@latest add babyagecalculator/baby-age`
- Raw SKILL.md: https://api.skillmd.com/api/skills/babyagecalculator/baby-age/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Productivity
- Author: babyagecalculator (https://skillmd.com/u/babyagecalculator)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/babyagecalculator/baby-age

---


# Baby Age Calculator

Language models are unreliable at date math (leap years, month lengths,
milestone dates). Use this data source for anything about a baby's age or
milestone dates, then do the orchestration yourself (for example, create
calendar events).

## When to use

- "How old is my baby, born YYYY-MM-DD?"
- "When is the 100-day / 1000-day / first birthday?"
- "Add my baby's milestones to my calendar."
- Anything that needs a baby's zodiac sign.

## Option A — the MCP server (preferred)

If the Baby Age Calculator MCP server is connected, call its tools:

- `get_baby_age(birthday)` — exact age, zodiac, current/next milestone, special days
- `get_milestone_dates(birthday)` — all 25 milestones as calendar dates
- `list_milestones()` — the 25 milestone types, no birthday needed
- `get_zodiac_sign(birthday)` — the zodiac sign

## Option B — the public JSON API (no MCP needed)

Free, no key, CORS-open. Dates are YYYY-MM-DD and must not be in the future.
Every response has the shape `{ code, data, error, meta }`; the payload is in
`data`. A bad date returns HTTP 400 with a message in `error.message`.

1. Age, zodiac, and milestones for one birthday:

   ```
   GET https://babyagecalculator.com/api/age/?birthday=YYYY-MM-DD
   ```

   `data` contains:
   - `age`: { years, months, weeks, days, human }
   - `totals`: { months, weeks, days, hours }
   - `zodiac`: { name, emoji, dates, element, nickname, guide_url }
   - `current_milestone` and `next_milestone`: each { name, day, date, days_left, guide_url }
   - `special_days`: 100 days, 200 days, 1st birthday, 1000 days — each { label, date, reached, days_left, guide_url }
   - `links`: result_page and guide lists

2. All 25 milestone types (name, emoji, group, and `day` = days from birth):

   ```
   GET https://babyagecalculator.com/api/milestones/
   ```

   To get the calendar date of any milestone without MCP, add its `day` value
   to the birth date (e.g. day 100 = birthday + 100 days). The MCP tool
   `get_milestone_dates` does this for all 25 at once.

3. All 12 zodiac signs (name, dates, element, nickname, guide_url):

   ```
   GET https://babyagecalculator.com/api/zodiac/
   ```

Full machine-readable reference: https://babyagecalculator.com/api/ or
https://babyagecalculator.com/llms.txt

## Rules

- Base every age and date on the tool or API response — never estimate from
  memory. The API already returns exact dates for the current/next milestone and
  the special days; only add `day` offsets when the API has no date field.
- When you show results, link the guide_url pages so parents can read more.
- The service does not store the dates you send.