Add days versus between dates
Between two dates counts workdays in the span under the holiday toggle you picked. Add/subtract applies N business days to a start date. Those are different questions; the page keeps them as two modes.
Your numbers
Workdays
Count workdays between two dates, or add workdays to a date. Federal holidays are optional.Business days
21Using the holiday and date choices aboveCalendar days30Elapsed days
Weekends skipped8Saturday and Sunday
Federal holidays skipped1Observed dates
How we got this
- Calendar-day spanElapsed days between the two dates30 days
- Weekend days excludedSaturday and Sunday8
- Federal holidays excludedObserved U.S. federal holidays1
What we assumed
- Saturday and Sunday are not counted as workdays.
- Federal holidays follow the usual observed federal schedule. Private, state, and local calendars can differ.
- The start and end date choices in the form are used as you set them.
Technical details
Method calendar-v1.0.0Data opm-federal-holiday-rules-2026-09
Discrepancy in the numbers? You can click Report incorrect result below or email hello@costanswer.com with the Method and Data lines.
Guide
Counting U.S. federal business days
Weekends are skipped. Federal holidays are optional using OPM’s holiday rules in the snapshot. State holidays, company shutdowns, and observed-versus-actual dates for a private employer are not inferred.
Questions about this calculator
Are state holidays included?
No. Only weekends and optional U.S. federal holidays from the OPM rules in the snapshot.
Do weekends count as business days?
No. Saturdays and Sundays are skipped. Optional federal holidays follow the OPM rules in the snapshot, not every state holiday.
Terms used here
- Business day
- A weekday that is not skipped as a federal holiday when that option is on.
- Observed holiday
- When a holiday falls on a weekend, federal offices often observe it on Friday or Monday. The snapshot’s rules decide that, not your company handbook.
Practical tips
Contract language that says “business days” may mean federal, banking, or local. Check the contract.
For calendar days including weekends, use the date or days-from-today calculators.
Limits and caveats
Exact under the holiday rules selected. Not a court-filing deadline calculator for every jurisdiction.
Results are for information. They are not legal, tax, medical, or financial advice. How the math is maintained · Report a wrong figure.
Engine notes
Rounding, versioning, and omissions that sit beside the guide rather than repeating it.
- Dates, not clock times. Dates are stored without a local time. Daylight saving cannot add or drop a day.
- Start and end dates. You choose whether the start and end dates count. Then weekends and holidays come out.
- Federal holidays. If a fixed holiday falls on Saturday it is usually observed Friday. If it falls on Sunday it is usually observed Monday.