Overview

April 17 is the 107th day of the year in the Gregorian calendar and the 108th in leap years. After April 17 there are 258 days remaining in a common year. The date falls toward the middle of April and is usually in the astrological sign of Aries (March 21–April 19).

Calendar position and technical notes

As part of the modern civil system, April 17 is placed within the Gregorian calendar, the internationally used calendar system. In years with an extra day in February (leap years) April 17 is counted one day later in the annual sequence; see more on leap-year rules at leap year and the structure of the calendar at Gregorian calendar.

Common observances and commemorations

Several international and national observances fall on or are celebrated on April 17. Most prominent among them is World Hemophilia Day, recognized by health organizations to raise awareness about bleeding disorders. Other observances can be national or local and sometimes shift when they coincide with weekends or holidays.

Notable historical events (examples)

  • Major political or military events: April 17, 1961, is known for the start of the Bay of Pigs invasion, a significant Cold War episode.
  • Cultural and scientific milestones: the date has hosted a variety of breakthroughs, dedications and first performances across different years.
  • Religious calendars and movable feasts: Easter and other movable dates sometimes fall on April 17, depending on lunar and ecclesiastical calculations; this changes year to year.

Uses and significance

Dates like April 17 serve as anchors for anniversaries, legal deadlines and seasonal planning. In some countries tax or administrative deadlines can fall on mid-April and are occasionally adjusted when public holidays affect the standard date. Commemorative observances—global health days, cultural festivals and historical anniversaries—use fixed dates to organize outreach and remembrance.

Distinctive facts

Although any calendar date repeats annually, particular days acquire special recognition through historical coincidence or organized campaigns. April 17 illustrates how a single date can be simultaneously ordinary (a point in the civil year) and notable (the marked anniversary of events or causes).