A date grid and a holiday collection have different sources. The grid is calculated from Gregorian rules; optional holiday entries come from a reviewed official dataset.
Calendar date calculations
Month lengths, weekdays and leap years are calculated from Gregorian date rules within 1900–2100. The published month and year pages use specific real dates rather than copied competitor calendar images. The U.S. Naval Observatory reference explains the calendar background.
These calculations do not supply institutional schedules, religious calendars or local observances. A date can exist in the grid while an optional holiday dataset has no reviewed information for that year.
U.S. federal holiday collection
Source: the U.S. Office of Personnel Management federal holiday tables and definitions. The records used for this collection were reviewed on October 27, 2026 for holiday years 2026, 2027 and 2028. The collection includes 33 holiday records, keeping the holiday date and standard observed date as separate fields.
The scope is U.S. federal statutory holidays and standard Monday-through-Friday observance. It does not claim every U.S. holiday, school closure, state or local date, religious observance or business schedule. A source can be official while still covering a narrower purpose than your own calendar.
Actual and observed dates
When the two dates differ, the calendar labels them separately. In 2027, Independence Day is July 4 and its standard observed date is July 5. New Year’s Day 2028 is January 1, while its observed date is December 31, 2027. The displayed date determines which month includes the entry.
When actual and observed dates are the same, the record does not create two unrelated holidays. Review the source and date-role labels when a holiday affects an important plan, and check the relevant organization’s own arrangements for closures or opening hours.
Coverage beyond the reviewed years
The 2028–2029 academic example contains valid dates in 2029, but this collection has not reviewed 2029 holiday records. The page and its output must keep that coverage note visible. An empty holiday area outside the reviewed range is not a complete list and does not mean there are no holidays.
Official sources may publish later years. Availability of a source is different from a completed review and integration into this collection. New records need their own source, actual/observed interpretation and review record before the coverage claim changes.
File format references
RFC 5545 is the reference for iCalendar date values and event boundaries, including exclusive DTEND for an all-day span. RFC 4180 describes common CSV field and quoting conventions. These references guide file structure; they do not define your event content or promise identical behavior in every receiving application.
Paper settings use explicit page dimensions. The W3C page-size reference documents the named A4 and Letter dimensions used in the layout discussion. Printing still requires a check of the selected printer, paper and scaling settings.
Dates you add yourself
Your own event titles, dates and notes remain separate from the official collection. Add a school closure, local observance or personal appointment using the source that applies to you. MonthSprig does not label those personal entries as verified OPM data merely because they appear beside a federal holiday.