Age Lab

Choose a calculator. Saved birthdays are optional; results stay in this session.

Device time12:00:00 p.m.Sat, Jan 1, 2000

Compare two birth dates

Compare the calendar age difference. Names are optional; birth times are ignored.

Show exampleHide example

Alex (15 Mar 2000) is 3 years, 6 months, 5 days older than Jordan (20 Sep 2003).

01 · Age difference

How much older or younger?

Pair 1

Person 1

Name optional

Birth date

Person 2

Name optional

Birth date

Age differenceEnter both birth dates to compare.

02 · Age comparison

Age on the reference date

CompareUses the reference birthday at this age. Optional months and days shift it.

Reference nameReference birth dateReference age

Reference dateWaiting for reference

Name to compare	Their birth date	Their age on this date
		Waiting for dates

03 · Age on a date

Everyone’s age on one meaningful date

Start with what you know

Reference date

Name	Birth date	Age (Y, M, D) on reference date
		Waiting for dates

04 · Age phase calculator

Which age phase is this person in?

Uses completed whole years, so the result stays stable between birthdays. Human labels are descriptive, not medical, legal, diagnostic, or maturity assessments.

Reference nameBirth dateReference date ()

Phase profileUse custom bands for this person

Custom bands are saved per selected birthday. Use the checkbox to apply them here; otherwise the detailed or broad profile is used. JSON backups include saved custom profiles.

Why these phases use these names

These are practical descriptive bands informed by common developmental and life-course language, not an official psychological classification or assessment. There is no universal set of age cutoffs: development varies by person, culture, and context, and research frameworks overlap. The calculator describes completed calendar age; it does not infer maturity, personality, capability, or mental health.

Current phaseWaiting for birth date

Completed ageWaiting for birth date

Phase transition—

Add a valid birth date to calculate a phase.

Phase	Age range	Begins	Next transition	Status
Infant	Under 1	—	No fixed end	Ready
Toddler	1–3	—	No fixed end	Ready
Early childhood	4–6	—	No fixed end	Ready
Middle childhood	7–9	—	No fixed end	Ready
Tween / preteen	10–12	—	No fixed end	Ready
Early adolescence	13–14	—	No fixed end	Ready
Later adolescence	15–17	—	No fixed end	Ready
Emerging adulthood	18–24	—	No fixed end	Ready
Young adulthood	25–34	—	No fixed end	Ready
Middle adulthood	35–49	—	No fixed end	Ready
Later adulthood	50–64	—	No fixed end	Ready
Older adulthood	65–74	—	No fixed end	Ready
Late older adulthood	75–84	—	No fixed end	Ready
Advanced older adulthood	85+	—	No fixed end	Ready

Age-term milestones

Common age terms, separate from phase labels; each band ends the day before the next begins.

Age term	Completed ages	Begins	End date	Status
Septuagenarian	70–79	—	—	Ready
Octogenarian	80–89	—	—	Ready
Nonagenarian	90–99	—	—	Ready
Centenarian	100–109	—	—	Ready
Supercentenarian	110+	—	—	Ready

05 · Age milestone calculator

When will this milestone happen?

Reference nameBirth date & timeEnter a date; time defaults to midnight.Time (optional)

Birth time is optional; without it, milestones use midnight.

The time-unit converter below can translate a milestone into another unit—for example, 1.5 days into 36 hours.

Unit	Target number	Milestone date	Countdown
years	Whole numbers only	Waiting for target	—
months	Whole numbers only	Waiting for target	—
weeks		Waiting for target	—
days		Waiting for target	—
hours		Waiting for target	—
minutes		Waiting for target	—
seconds		Waiting for target	—