Date Calculator
Find the exact number of days, weeks, and months between two dates.
How this calculator counts days
The day count is inclusive of the difference between the two calendar dates. Weeks are the day total divided by seven, and the month figure is an approximation based on average month length.
Practical uses for date calculations
Date calculations are commonly needed for project planning (how many days until a deadline), legal and contract purposes (calculating notice periods), and personal milestones (counting down to an event or anniversary).
Because month lengths vary and leap years add complexity, manual date math is a common source of small errors — using a calculator that works from actual calendar dates avoids these mistakes entirely.
A worked example
From January 15 to June 30 of the same year: that's 166 days, or about 23.7 weeks, or roughly 5.5 months.
Across a year boundary — from November 1 to February 14 — the span is 105 days, correctly accounting for the transition into the new year without requiring any manual adjustment.
Common uses for date difference calculations
Calculating the exact number of days between two dates comes up in contexts like determining project timelines, calculating age in days for medical or legal purposes, figuring out how many days until an event, or determining contract or lease durations precisely.
Because months vary in length and leap years add complexity, manual date-difference calculations are error-prone — using a calculator that works from actual calendar dates avoids the common mistakes of assuming every month has 30 days or forgetting leap years.
Frequently asked questions
Does this account for leap years?
Yes — the calculation uses actual calendar dates, so leap years are automatically accounted for.
Can the end date be before the start date?
Enter the earlier date as the start date for an accurate positive day count.
Does this calculation include or exclude the start date?
The day count reflects the calendar difference between the two dates — if you need an inclusive count (counting both the start and end day), add one to the result.
How accurate is the month estimate shown?
The month figure uses an average month length (30.44 days) for approximation — for exact month/day breakdowns, a dedicated year/month/day age-style calculation is more precise.
Does this calculator account for leap years automatically?
Yes — since it works from actual calendar dates rather than approximations, leap years are automatically factored into the day count.