Methods, Sources & Assumptions
A date counts when its weekday is selected and it is neither an excluded observed holiday nor a custom closure. The range mode honors both endpoint switches. Add/subtract treats the starting date as day zero. Calendar-date arithmetic uses UTC day numbers, so a local daylight-saving transition does not shorten or lengthen the count.
Federal observed holidays are generated from recurring rules for adjacent years too. This captures New Year’s Day 2028 observed on December 31, 2027. Juneteenth begins in the preset in 2021. The preset follows standard Monday–Friday observance and does not include one-off closures or universalize Inauguration Day.
Worked check: November 9–13, 2026, excluding the start and including the end, gives four Monday–Friday days without holidays, or three with Veterans Day excluded. Adding five federal-calendar working days to November 9 gives November 17.
What the result means
Results are planning estimates. Unrounded values are used in the calculations; rounding is applied for display and whole purchasing units. Changing the unit system resets example values rather than silently treating old numbers as different units. The calculator rejects invalid dimensions and impossible combinations.
Sources
- OPM Federal Holidays
- OPM Holidays Work Schedules and Pay
- OPM Federal Holidays — In Lieu Of Determination
- U.S. Naval Observatory: Daylight Saving Time
- U.S. Naval Observatory: Leap Years
- MDN Date.UTC
Corrections
Found a calculation or explanation that needs attention? Send the inputs, expected answer and a source if available. Please do not send sensitive personal information.