Billion Second Birthday

Find out exactly when you turn 1,000,000,000 seconds old.

Enter your birth date, optional time, and timezone — and the calculator tells you your billionth second birthday to the second, accounting for leap years and leap seconds.

Features

• Live age-in-seconds counter (updates every 50ms)
• Accurate leap second calculation (all 27 UTC leap seconds since 1972)
• Arbitrary IANA timezone support
• Add to Google Calendar or download a .ics file (for future billionth seconds)
• Share via Web Share API or clipboard fallback
• Localized for 19 languages with RTL support (Arabic)
• Accessible (WCAG-compliant, ARIA, keyboard navigation)
• Mobile-friendly dark UI

Tech Stack

• Svelte 5 + TypeScript
• Vite
• Tailwind CSS v4

Development

pnpm install
pnpm dev

Build

pnpm build
pnpm preview