Methodology & sources

Federal holidays: Office of Personnel Management rules, with the observed date moved to Friday or Monday when a holiday falls on a weekend. The rule is applied to the legal date, not copied from a third-party list.

Tax deadlines: the Internal Revenue Service calendar for the current tax year. Where a date falls on a weekend or a holiday, the effective date is the next business day, and that is the date we publish.

Exam sessions: the College Board and ACT publish their own national calendars. Test dates, registration deadlines, late-registration windows and score release dates are read from those pages, and the PSAT is treated separately because each school chooses its own day inside the window.

School calendars: the district’s official HTML page or PDF, downloaded automatically and converted to text. Every published date is compared line by line with the source; a mismatch blocks the update, and unreviewed districts stay at “collecting” with no dates shown.

When a district revises its calendar during the year, the page is updated and the verification date changes. Dates that cannot be re-checked are removed rather than left in place.

• Primary sources only, never an aggregator.
• Verification date shown next to the source.
• No date calculated without an explicit rule.
• A district with no verified source shows no dates at all.