Date Calculator
Days between two dates, add or subtract days/weeks/months/years, and instantly answer"what is 90 days from today?". Handles leap years automatically.
Calculate dates
Two modes: difference between dates, or add/subtract from a date.
Common date calculations
- 90 days from today — a standard notice period for contracts and many legal deadlines
- 30 / 60 / 90 days — typical review, refund, or notice windows
- Days between two dates — trip length, project duration, or age in days
- Date before a deadline — "what date was 14 days ago?"
How the calculation works
The calculator converts both dates to timestamps and subtracts them, dividing by the number of milliseconds in a day (86,400,000). Your browser's native date engine handles leap years, month lengths, and daylight-saving shifts, so the result is accurate to the day. For adding months or years, the calculator adjusts the calendar month or year directly, clamping the day-of-month when the target month is shorter (e.g., Jan 31 + 1 month = Feb 28).
Related tools
- Days Until Calculator — live countdown to any date
- Christmas Countdown
- Age Calculator — your exact age in years, months, and days
Frequently asked questions
How do I calculate days between two dates?+
Enter a start date and an end date, and the calculator shows the exact number of days (and weeks) between them — including the time in years, months, and days. It counts calendar days, so a leap year is handled automatically.
What is 90 days from today?+
Pick today as the start date and add 90 days, or use the quick 'Add days' mode with +90. The calculator gives you the exact future date. For reference, 90 days is roughly 3 months, and 30/60/90 days are common deadlines in contracts, notices, and exam schedules.
How do I add days to a date?+
Use the 'Add / subtract' mode. Enter a starting date, choose to add (or subtract) a number of days, weeks, months or years, and the calculator returns the resulting date. This is useful for 'what date is 30 days from now?' or 'what date was 100 days ago?'.
Is the date calculator accurate across leap years?+
Yes. The calculation uses your browser's native date handling, which accounts for leap years, month lengths (28/30/31 days), and daylight saving time. A date difference spanning February in a leap year is handled correctly.
Can I calculate business days (excluding weekends)?+
This calculator counts calendar days. For working/business days that exclude weekends and holidays, you'd need a dedicated business-day calculator — but for most uses (deadlines, age, countdowns) calendar days are what matters.
What's the difference between this and a countdown?+
A countdown (like our Days Until tool) ticks down in real time to a single future date. This date calculator works with two dates or a date + offset, giving you the precise difference or resulting date instantly. Use the Days Until calculator for live countdowns to Christmas, exams, or trips.