Ever tried to figure out what date it’ll be 90 days from now? Or maybe you need to know what day it was exactly 6 months ago when that thing happened? Your brain does the math wrong. This calculator doesn’t.

What it does: You pick a date, add or subtract any amount of time (days, weeks, months, years), and it tells you the exact date you’ll land on. It’s basically a time machine but for calendars.

Using it is stupidly simple:

First, pick whether you want to add or subtract time. Two buttons at the top. “Add Time” or “Subtract Time.” Click one. Then enter your starting date. Today, yesterday, your wedding anniversary, whatever. Next, type in how much time you want to jump. Could be 45 days. Could be 3 months. Could be 2 years.

Choose your unit from the dropdown. Days, weeks, months, or years. Hit “Calculate Date.” Done. The calculator shows you the exact date you’ll land on, what day of the week it is, and displays it big and bold so you can screenshot it for proof.

Why this matters more than you think:

Your landlord wants rent “30 days from today.” What date is that exactly? Check. You made a bet with your friend that something would happen “in exactly 100 days.” Need to mark your calendar? Check. That promotion your boss promised “in 6 months” when is that actually? October 27th, apparently.

Real talk: This calculator has saved more arguments than couples therapy. Someone says “I told you three weeks ago” and you’re sure it was longer? Go back three weeks from today and see what date that is. Now you have facts, not feelings.

The best part? You can toggle between adding and subtracting without starting over. Made a mistake? Switch the button and try again. The interface remembers your date and amount. It’s like it knows you’re going to change your mind.