Anniversary Date Calculator
Find every 100-day milestone and yearly anniversary from a single start date
Pick the date you started dating, got married, or launched your business, and this calculator counts it as day 1 to work out every milestone from 100 days through 5,000 days, plus every anniversary from year 1 to year 20, with a countdown for each one. It's handy for couples, newlyweds, and business owners who want plenty of warning before the next big date rolls around, and the date you enter is calculated entirely in your browser and never sent to a server.
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🔒 Everything runs 100% in your browser. Your files and input are never uploaded to any server.
How to use
- Choose your start date (day 1) in the calendar field.
- Check the 100-day milestone list to see the exact date and countdown for each one.
- Scroll through the yearly anniversaries from year 1 to year 20.
- Hit "Copy all results" to grab the whole list as plain text.
FAQ
- Why does the 100-day mark land 99 days after my start date?
- The start date counts as day 1, so day 100 falls 99 days after it.
- Can I use it for a wedding or business anniversary?
- Yes. Set your wedding day or launch day as the start date and the yearly anniversaries are calculated exactly the same way.
- Does the yearly anniversary date stay accurate across leap years?
- Yes, the calculation is based on real calendar dates, so it stays accurate even when a leap year with February 29 falls in between. The one special case is when the start date itself is February 29 — since that date doesn't exist in non-leap years, the anniversary is shown as either February 28 or March 1 instead.