BCBetter Calculators

Time Duration Calculator

Calculate the number of days and weeks between two dates.

🧮

Enter your values and click Calculate

How It Works

Both dates are validated then converted to UTC midnight timestamps to eliminate errors caused by Daylight Saving Time transitions — since DST can shift local clocks by an hour, using UTC prevents a 23-hour or 25-hour day from distorting the result. The absolute difference in milliseconds is divided by 86,400,000 (the number of milliseconds in one day) and rounded to get total days. Weeks are calculated as days ÷ 7, rounded to two decimal places. Approximate months use days ÷ 30.4375, which is the average calendar month length derived from 365.25 ÷ 12. The absolute value is used throughout so results are always positive regardless of which date is entered first, making the order of input irrelevant. Invalid dates such as February 30 are rejected by cross-checking the computed date components against the inputs.

Examples

January 1 to December 31, 2025
The length of a full calendar year from first to last day.
Result: 364 days — 52 weeks — approximately 11.96 months.
March 1 to May 29, 2025
A 90-day project sprint or lease period.
Result: 89 days — 12.71 weeks — approximately 2.92 months.
June 15, 2023 to June 15, 2025
An exact two-year span for a contract or anniversary.
Result: 730 days — 104.29 weeks — approximately 23.99 months.

Frequently Asked Questions

Does the result include both the start and end dates?
No. The calculator measures the gap between two dates. January 1 to January 2 is 1 day. If you need to count both endpoints (inclusive), add 1 to the result.
What if I enter the end date before the start date?
The result is always a positive number regardless of which date is entered first. The calculator uses the absolute difference, so the order of the dates does not affect the output.
Why does the approximate months calculation sometimes give a decimal?
Months are calculated by dividing total days by 30.4375, which is the average length of a calendar month (365.25 ÷ 12). Because months vary in length from 28 to 31 days, a pure day-to-month conversion always involves an approximation.

Related Calculators

life✨

Date Subtract

Subtract a number of days, weeks, or months from a date to find an earlier date.

Calculate →
life✨

Work Hours

Calculate how many hours you worked in a day after accounting for breaks.

Calculate →
life✨

Age Difference

Calculate the age difference between two birthdays in years, months, and days.

Calculate →