Date Calculator

About

Date Calculator is a tiny, fast browser tool for the date math you keep doing in your head — without leaving the tab you're on.

Open the popup, type a date in whatever format you usually write it, and get an answer immediately. No spreadsheet, no calendar app, no "what day of the week is that?" guesswork.

What you can do

• Add or subtract any number of days, weeks, months, or years from a starting date
• Find the difference between two dates — exact day count plus a weeks-and-months breakdown
• Switch between calendar days and business days (skips weekends)
• Bring your own custom holidays so business-day math matches your team's calendar
• One-click swap for From / To dates in the Difference tab

Built to stay out of your way

• Flexible date input — 01/15/2026, 1-15-2026, Jan 15, 2026, 15 January 2026, 2026-01-15, and more all just work
• Year-less shorthand — type Jan 15 or 1/15 and it assumes this year, then fills the year in for you
• Today button on every date field for one-tap "now"
• Calendar picker if you'd rather click than type
• Copy results in short, long, or weekday format with one click
• Highlight a date on any page, right-click → Send to Date Calculator to pre-fill it

Make it yours

• Light, dark, or system theme
• Configurable default amount and unit for the Add / Subtract tab
• Settings sync across your Chrome profile

Privacy

No accounts, no tracking, no network calls. Everything runs locally in your browser. Settings are stored in Chrome's built-in sync storage.