Date Calculator — Add, Subtract, and Compare Dates Easily
Find out what date falls 90 days from now, or how many days are between two dates — instantly, without counting on a calendar.
Date math comes up more often than you'd think: figuring out a deadline 30 days from today, calculating how many days until an event, or determining how long a project has been running.
Our Date Calculator supports two common operations: calculating the difference between two dates (in days, and optionally weeks/months/years), and adding or subtracting a number of days from a starting date to find a resulting date.
🛠 Ready to try it? Use the Date Calculator now — free, no signup required.
Open Date Calculator →How to Use the Date Calculator
- Open the Date Calculator tool.
- Choose whether you want to find the difference between two dates, or add/subtract days from a date.
- For date difference: enter both the start and end dates.
- For add/subtract: enter a starting date and the number of days to add or subtract.
- View the calculated result instantly.
Common Use Cases
- Calculating a project deadline that falls a certain number of days from the start date.
- Finding out how many days are left until an event, holiday, or due date.
- Calculating the number of days between an invoice date and its due date.
- Determining what date falls a certain number of business days from today.
- Calculating contract or subscription end dates from a start date plus duration.
Frequently Asked Questions
Does the calculator account for different month lengths?
Yes, the calculation correctly handles months with different numbers of days (28-31) as well as leap years when computing date differences or adding/subtracting days.
Can I subtract days to get a past date?
Yes, entering a negative number of days (or selecting 'subtract') will calculate a date that falls before the starting date.
Does the date difference include both the start and end date?
Typically, the difference is calculated as the number of days between the two dates (exclusive of one endpoint), which matches how most 'days until' calculations work — check the result against your specific use case if exact inclusive/exclusive counting matters.
Can I calculate differences in weeks, months, or years instead of just days?
If the tool provides this breakdown, the total day difference can also be expressed in larger units — otherwise, you can convert manually (e.g., divide days by 7 for weeks).
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Open Date Calculator →