- Days
- 281
- Weeks
- 40.14
How it works
Repeated months can drift
Starting January 31, 2026, adding one month twice gives March 28 under this tool’s month-end rule. Adding two months at once gives March 31. Choose whether a recurring schedule follows the original date or each previous result.
Choosing elapsed days or business days
From January 1 to January 3, the elapsed calendar difference is 2 days; including the end date gives 3 counted dates. Adding one calendar month to January 31, 2026 gives February 28, because this tool clamps to the last available day rather than treating a month as 30 days. For business dates, use the standard Monday–Friday mode or choose working weekdays in the custom mode. Custom modes also support the stated holiday preset and additional exclusions; check the selected calendar before using a deadline.
Between two dates: formula and assumptions
Calendar-day difference uses date-only values, independent of daylight-saving changes.
Results are signed if the end precedes the start. Including the end date adds one day in the direction of the interval.
Add or subtract time: formula and assumptions
Apply calendar years and months, clamp the day to month end, then add weeks and days.
Use negative quantities to subtract. Calendar months are not treated as a fixed number of days.
Business days: formula and assumptions
Count Monday through Friday, excluding supplied holiday dates.
The start date is included; the end date is excluded unless selected. Weekends and supplied holidays are counted once.
Add business days: formula and assumptions
Move forward or backward, skipping Saturdays, Sundays, and the supplied holidays.
The starting date is not counted. Negative quantities subtract business days; zero leaves the date unchanged.
Custom business-day count: formula and assumptions
Count selected working weekdays that are not excluded holidays.
Date-only Gregorian arithmetic. Start-inclusive and end-exclusive unless selected. Reverse ranges return a signed count.
Add custom business days: formula and assumptions
Move one calendar day at a time and count only working dates.
The starting date is excluded. Negative values subtract business days. Zero leaves the date unchanged.
Worked example
Using the Between two dates example:
- Start date
- 2026-01-01
- End date
- 2026-10-09
- Include end date
- No
Calendar-day difference uses date-only values, independent of daylight-saving changes.
Example result
Days: 281
Weeks: 40.14
These are illustrative inputs. Change the values to explore a different scenario.
Formula references
References explain the underlying methods; they do not imply endorsement or individual professional review of Finflo.
Common questions
Does adding one month mean adding 30 days?
No. Calendar-month arithmetic changes the month and clamps an unavailable day to month end before adding weeks or days.
Are public holidays excluded automatically?
The standard business-day modes exclude the holiday dates you supply. Custom business-day modes can also apply the listed holiday preset, selected holiday rules, recurring exclusions, and chosen working weekdays. No preset automatically represents every employer or local calendar.
Prepared by Finflo. See our methodology and editorial policy.