Date Calculator

When to use Date Calculator

Your lease says you must give 90 days written notice before vacating, and you want to know the last day you can send that letter before your planned move-out date. Switch to add/subtract mode, enter your target move-out date, subtract 90 days, and the calculator lands on the deadline. Flip to difference mode to ask the other direction: how many days remain on a 180-day software trial, a 30-day return window, or a visa countdown. The calculator handles month boundaries and leap years correctly using the browser's Date API, so February math comes out right. Useful also for project managers counting business milestones, parents figuring out a summer camp end date, or anyone who hates counting squares on a paper calendar.

• Find the last day to give 90-day lease notice before move-out
• Count remaining days on a 180-day software trial
• Calculate when a 10-week medication course ends from today

About this tool

Counting down to a due date, a contract deadline, or a visa expiry? Pick two dates and get the exact difference in days, weeks, months, and years. Or flip to add/subtract mode: start from any date, add or subtract a number of days, and land on the result — useful for calculating a 90-day notice period, a 30-day return window, or when a medication course ends. The calculator handles leap years and month boundaries correctly. Processing stays on your device — no inputs are stored or sent anywhere.