Date Calculator

Calculate the number of days between two dates, or add/subtract days, weeks, months, or years from a date.

mode Choose whether to count days between two dates or add/subtract time from a date.

Start Date The starting date for your calculation.

End Date The ending date, used when counting days between two dates.

Days Days to add (positive) or subtract (negative).

Months Months to add (positive) or subtract (negative).

Years Years to add (positive) or subtract (negative).

Days Between 7.00 (7 days)

Start Date 2026-10-17

End Date 2026-10-24

Editorial Standard

GetCalcu Methodology & Editorial Standards

Reviewed: September 2026

ISO 80000 mathematical sign standards and deterministic algebraic formulas.

Reference Sources: GetCalcu Mathematical Review Board

How to Calculate Days Between Dates and Add or Subtract Time

From project deadlines to pregnancy due dates and contract terms, calculating time spans accurately matters. The GetCalcu Date Calculator counts the days between two dates or adds and subtracts days, months, and years from any starting date — accounting for real calendar rules.

Counting Days Between Two Dates

The calculator finds the absolute difference between the start and end dates, counting full days. It correctly handles months of different lengths and leap years, so February 28 to March 1 is always 1 day (or 2 in a non-leap year bridge).

Adding and Subtracting Calendar Units

When adding months or years, the calculator follows calendar arithmetic — adding 1 month to January 31 gives February 28 (or 29 in a leap year), not March 3. This matches how contracts and due dates are typically calculated.

How to Use the Date Calculator

1
Choose a mode: "Days between dates" or "Add/subtract from date".
2
For days between: pick a start date and an end date.
3
For add/subtract: enter a start date, then the days, months, and years to add or subtract (use negative numbers to subtract).
4
Read the result — total days, weeks, months, and the resulting date.
5
Adjust the inputs to explore different scenarios.

Date Calculator Formula

Days Between = |End Date − Start Date| | Result Date = Start Date + Days + Months + Years (calendar arithmetic)

Real-World Worked Examples

These scenarios demonstrate how key input parameters alter your calculation outcome.

Project Duration

Input: Mode: Days between | Start: 2025-01-15, End: 2025-04-20

Result: 95 days (~13.6 weeks)

90-Day Deadline

Input: Mode: Add | Start: 2025-03-01, Add 90 days

Result: Due date: 2025-05-30

Frequently Asked Questions

How do I calculate the number of days between two dates?

To calculate days between two dates, subtract the earlier date from the later date. The result is the number of full days between them. Our calculator does this instantly and also converts the span into weeks and months for context.

How many days are in a month on average?

Averaged over a 4-year leap cycle, a month is 30.4375 days (365.25 ÷ 12). For quick estimates, 30 days per month is common, but exact day counts depend on the specific months involved. Our calculator uses exact calendar dates for precision.

Does the date calculator account for leap years?

Yes. The calculator uses real calendar arithmetic, so it correctly includes February 29 in leap years. For example, the days between February 28, 2024 and March 1, 2024 is 2 days because 2024 is a leap year.

How do I add months to a date that does not exist?

When adding months lands on a date that does not exist (like January 31 + 1 month = February 31), calendar arithmetic rolls back to the last valid day of the target month — February 28 or 29. Our calculator follows this standard convention.

How do I count business days instead of calendar days?

This calculator counts all calendar days. To count only business days (Monday–Friday), exclude weekends manually, or subtract 2 days for every full 7-day week in the span. A dedicated business-day calculator that excludes holidays is best for precise working-day counts.