Why doesn’t “months and days” match the total divided by 30?

Because calendar months are not equal. The breakdown walks the calendar rather than averaging, so 31 January to 28 February comes out as 0 months and 28 days, while 1 March to 1 April is exactly 1 month. Dividing by 30 gives you a mean month, and the two answers drift further apart the longer the span.

What date range does it accept?

Years 0100 to 9999. A shift landing outside that is refused rather than quietly wrapped.

Date Difference

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What do you want to work out?Start dateUsed by both modesEnd dateDifference mode onlyAmountAdd / subtract mode onlyUnitDirection

From Thu, 1 Jan 2026 to Fri, 25 Dec 2026.
Unit	Total
Days	358
Weeks	51.14
Whole months	11
Weekdays (Mon–Fri)	256
Weekend days	102
Hours	8,592
Minutes	515,520

How it works

Date Difference Calculator and Date Adder

Work out the exact gap between two dates, in years, months and days, in plain days, or in weekdays only, then flip to the other mode to add or subtract days, weeks, months or years from a date.

What this does

Difference given as a calendar breakdown alongside the raw day count
Weekday-only total that counts the start day and leaves out the end day
Weekend days and whole weeks broken out separately
Second mode adds or subtracts days, weeks, months or years from a date
Month and year shifts clamp to the last valid day, so 31 January plus a month lands on 28 February
Dates are handled as UTC timestamps, so no daylight-saving change can move a day boundary

FAQ

Neither, by default. The headline total is the plain gap, so 1 January to 2 January is one day, and the line underneath gives you the inclusive count if you need it. The weekday figure follows a different rule again: it counts the start day and excludes the end day, which is the convention notice periods and delivery estimates usually run on.

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