Time Duration Calculator

Enter a start date and end date using separate year, month, and day fields to find the exact number of days, weeks, and approximate months between them. Both dates are converted to UTC midnight so that daylight saving time changes do not affect the result. The result is always positive regardless of which date you enter first. Useful for project planning, countdown timers, lease and contract durations, event scheduling, travel itineraries, or any situation where you need a precise date range expressed in multiple time units. The calculator also validates that each date actually exists on the calendar — invalid dates like February 30 or April 31 are rejected rather than silently shifted to the nearest valid date, ensuring you always get a meaningful and correct result. Whether you are calculating the length of a 6-month lease, the number of days until a product launch, or the duration of a past project to report on a timesheet, entering the two boundary dates gives you an instant breakdown in three complementary time units: days for precision, weeks for sprint planning, and months for high-level scheduling.

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.