LifeSpan

Know Your Time

People Google "how many days have I been alive" millions of times a month. Every result is a 2009-era tool with ads, low contrast, and zero personality. LifeSpan is the answer those searches deserve — fast, accurate, shareable, and genuinely useful beyond a single number.

Features

Precise Age

Years, months, days, hours — all computed live with no rounding.

Life Progress

A progress bar benchmarked to 80 years showing how far you've come.

Milestones

Ages 18–70 with past/upcoming/future status and days until each.

Remaining Timeline

A year-by-year grid of your life — every block is one year.

Birthday Countdown

Live ticking countdown to your next birthday, leap-day safe.

Shareable URLs

Every birth date gets a permanent URL with a dynamic OG image.

Tech stack

Next.js 15

App Router, RSC, edge-ready

Tailwind CSS

Utility-first, no runtime

next-themes

Dark/light mode, SSR-safe

TypeScript

All date logic, zero deps

Vercel

Edge functions, OG images

API Reference

All calculation logic lives in lib/ as pure TypeScript functions — no framework dependencies, fully importable in any Node.js or edge environment.

lib/age

calculateAge

calculateAge(birthDate: string | Date, referenceDate?: string | Date): AgeResult

Returns exact age broken down into years, months, days, and total months.

Example

import { calculateAge } from "@/lib/age";

const result = calculateAge("1990-05-14");

if (result.isValid) {
  console.log(result.years);       // e.g. 34
  console.log(result.months);      // e.g. 7
  console.log(result.days);        // e.g. 3
  console.log(result.totalMonths); // e.g. 415
}

Success response

{
  isValid: true,
  birthDate: "1990-05-14",
  referenceDate: "2025-01-17",
  years: 34,
  months: 7,
  days: 3,
  totalMonths: 415
}

Error response

{
  isValid: false,
  error: "FUTURE_DATE" | "INVALID_DATE",
  message: "Birth date cannot be in the future."
}

calculateDaysAlive

calculateDaysAlive(birthDate: string | Date, referenceDate?: string | Date): DaysAliveResult

Returns the total number of days elapsed since birth.

Example

import { calculateDaysAlive } from "@/lib/age";

const result = calculateDaysAlive("1990-05-14");

if (result.isValid) {
  console.log(result.daysAlive); // e.g. 12666
}

Success response

{
  isValid: true,
  birthDate: "1990-05-14",
  referenceDate: "2025-01-17",
  daysAlive: 12666
}

calculateWeeksAlive

calculateWeeksAlive(birthDate: string | Date, referenceDate?: string | Date): WeeksAliveResult

Returns total complete weeks alive and leftover days.

Example

import { calculateWeeksAlive } from "@/lib/age";

const result = calculateWeeksAlive("1990-05-14");

if (result.isValid) {
  console.log(result.weeksAlive);    // e.g. 1809
  console.log(result.remainingDays); // e.g. 3
}

Success response

{
  isValid: true,
  birthDate: "1990-05-14",
  referenceDate: "2025-01-17",
  weeksAlive: 1809,
  remainingDays: 3
}

calculateHoursAlive

calculateHoursAlive(birthDate: string | Date, referenceDate?: string | Date): HoursAliveResult

Returns total hours alive (days × 24, no partial hours).

Example

import { calculateHoursAlive } from "@/lib/age";

const result = calculateHoursAlive("1990-05-14");

if (result.isValid) {
  console.log(result.hoursAlive); // e.g. 303984
}

Success response

{
  isValid: true,
  birthDate: "1990-05-14",
  referenceDate: "2025-01-17",
  hoursAlive: 303984
}

lib/milestones

calculateMilestones

calculateMilestones(birthDate: string | Date, referenceDate?: string | Date): MilestoneTimelineResult

Returns milestone dates for ages 18, 21, 25, 30, 40, 50, 60, 70 — each tagged as Passed, Upcoming, or Future.

Example

import { calculateMilestones } from "@/lib/milestones";

const result = calculateMilestones("1990-05-14");

if (result.isValid) {
  result.milestones.forEach((m) => {
    console.log(m.age, m.dateReached, m.status);
    // 18  "2008-05-14"  "Passed"
    // 25  "2015-05-14"  "Passed"
    // 35  "2025-05-14"  "Upcoming"
    // 40  "2030-05-14"  "Future"
  });
}

Success response

{
  isValid: true,
  birthDate: "1990-05-14",
  referenceDate: "2025-01-17",
  milestones: [
    { age: 18, dateReached: "2008-05-14", status: "Passed" },
    { age: 21, dateReached: "2011-05-14", status: "Passed" },
    { age: 25, dateReached: "2015-05-14", status: "Passed" },
    { age: 30, dateReached: "2020-05-14", status: "Passed" },
    { age: 40, dateReached: "2030-05-14", status: "Upcoming" },
    ...
  ]
}

lib/facts

calculateFunFacts

calculateFunFacts(birthDate: string | Date, referenceDate?: string | Date): FunFactsResult

Returns biological estimates — heartbeats, breaths, sleep hours — and the weekday you were born on.

Example

import { calculateFunFacts } from "@/lib/facts";

const result = calculateFunFacts("1990-05-14");

if (result.isValid) {
  console.log(result.estimatedHeartbeats); // e.g. 1,274,788,800
  console.log(result.estimatedBreaths);    // e.g. 291,149,568
  console.log(result.estimatedSleepHours); // e.g. 101,328
  console.log(result.birthWeekday);        // e.g. "Monday"
}

Success response

{
  isValid: true,
  birthDate: "1990-05-14",
  referenceDate: "2025-01-17",
  estimatedHeartbeats: 1274788800,
  estimatedBreaths: 291149568,
  estimatedSleepHours: 101328,
  birthWeekday: "Monday",
  assumptions: {
    heartRateBpm: 70,
    breathsPerMinute: 16,
    sleepHoursPerDay: 8
  }
}

Error handling pattern

Every function returns a discriminated union — always check isValid before accessing result fields. Errors carry a typed error code ("INVALID_DATE" or "FUTURE_DATE") plus a human-readable message.

const result = calculateAge(userInput);

if (!result.isValid) {
  // result.error  → "INVALID_DATE" | "FUTURE_DATE"
  // result.message → human-readable string
  showError(result.message);
  return;
}

// Safe to access result.years, result.months, etc.

Shareable URL pattern

Any valid ISO date maps to a permanent page with a dynamic OG image generated at the CDN edge.

// Page route
https://lifespan.app/age/1990-05-14

// Dynamic OG image (auto-generated)
https://lifespan.app/age/1990-05-14/opengraph-image

Your data stays yours

LifeSpan stores nothing. All calculations happen entirely in your browser. Your birth date is never sent to any server — it only appears in the URL if you choose to share it.

Calculate your age →

Features

Precise Age

Years, months, days, hours — all computed live with no rounding.

Life Progress

A progress bar benchmarked to 80 years showing how far you've come.

Milestones

Ages 18–70 with past/upcoming/future status and days until each.

Remaining Timeline

A year-by-year grid of your life — every block is one year.

Birthday Countdown

Live ticking countdown to your next birthday, leap-day safe.

Shareable URLs

Every birth date gets a permanent URL with a dynamic OG image.

import { calculateAge } from "@/lib/age"; const result = calculateAge("1990-05-14"); if (result.isValid) { console.log(result.years); // e.g. 34 console.log(result.months); // e.g. 7 console.log(result.days); // e.g. 3 console.log(result.totalMonths); // e.g. 415 }

import { calculateWeeksAlive } from "@/lib/age"; const result = calculateWeeksAlive("1990-05-14"); if (result.isValid) { console.log(result.weeksAlive); // e.g. 1809 console.log(result.remainingDays); // e.g. 3 }

import { calculateMilestones } from "@/lib/milestones"; const result = calculateMilestones("1990-05-14"); if (result.isValid) { result.milestones.forEach((m) => { console.log(m.age, m.dateReached, m.status); // 18 "2008-05-14" "Passed" // 25 "2015-05-14" "Passed" // 35 "2025-05-14" "Upcoming" // 40 "2030-05-14" "Future" }); }

{ isValid: true, birthDate: "1990-05-14", referenceDate: "2025-01-17", milestones: [ { age: 18, dateReached: "2008-05-14", status: "Passed" }, { age: 21, dateReached: "2011-05-14", status: "Passed" }, { age: 25, dateReached: "2015-05-14", status: "Passed" }, { age: 30, dateReached: "2020-05-14", status: "Passed" }, { age: 40, dateReached: "2030-05-14", status: "Upcoming" }, ... ] }

import { calculateFunFacts } from "@/lib/facts"; const result = calculateFunFacts("1990-05-14"); if (result.isValid) { console.log(result.estimatedHeartbeats); // e.g. 1,274,788,800 console.log(result.estimatedBreaths); // e.g. 291,149,568 console.log(result.estimatedSleepHours); // e.g. 101,328 console.log(result.birthWeekday); // e.g. "Monday" }

{ isValid: true, birthDate: "1990-05-14", referenceDate: "2025-01-17", estimatedHeartbeats: 1274788800, estimatedBreaths: 291149568, estimatedSleepHours: 101328, birthWeekday: "Monday", assumptions: { heartRateBpm: 70, breathsPerMinute: 16, sleepHoursPerDay: 8 } }

const result = calculateAge(userInput); if (!result.isValid) { // result.error → "INVALID_DATE" | "FUTURE_DATE" // result.message → human-readable string showError(result.message); return; } // Safe to access result.years, result.months, etc.