Holiday and closure differences
A federal holiday does not automatically close every school, bank, court, business or state office. Religious and cultural observances can begin at sundown or vary by local practice. Islamic dates may differ by a day where communities rely on physical moon sighting.
Astronomical times
Moon phases and seasonal events are calculated estimates shown in the stated time zone. A moment near midnight can appear on a different calendar date elsewhere. Use NASA, the US Naval Observatory or a local astronomical service for observation planning that requires higher precision.
Historical calendars
The site uses the Gregorian calendar for its supported modern years. For older historical documents, remember that countries adopted the Gregorian system at different times and that contemporary records may use Old Style dates.