Is 2028 A Leap Year?

Yes, 2028 is a leap year. The Gregorian leap-year rule has three sequential tests: (1) divisible by 4? -> if no, common year; (2) divisible by 100? -> if no, leap year (stop); (3) divisible by 400? -> if yes, leap year; if no, common year. Year 2028 / 4 = 507, an integer, so test 1 passes. 2028 mod 100 = 28, not zero, so test 2 says ‘not a century year, declare leap’. We never reach test 3. So 2028 has 366 days, February 2028 has 29 days, and 29 February 2028 falls on a Tuesday.

The rule was ratified by Pope Gregory XIII's bull Inter gravissimas on 24 February 1582 in Vatican City. Pope Gregory's astronomers - chiefly Christopher Clavius of the Roman College and Aloysius Lilius (the Italian physician whose calendar reform proposal had been the basis for the bull) - proved mathematically that the Julian leap rule (every fourth year, no exceptions) made the average year 365.25 days, which overshoots the true tropical year (365.2422 days) by 11 minutes 14 seconds per year. The Gregorian rule trims three leap days every 400 years, giving an average year length of 365.2425 days - within 26 seconds of true.

Before 1582, Europe used the Julian calendar, introduced by Julius Caesar in 45 BCE on the advice of the Alexandrian astronomer Sosigenes. The Julian year had 365.25 days exactly, with a leap day every fourth year without exception. This drifted about three days every 400 years against the seasons. By 1582 the Julian calendar lagged the equinox by ten days, so Pope Gregory dropped ten days from October 1582 (4 October 1582 was followed by 15 October 1582) and tightened the leap rule.

Different countries adopted the Gregorian reform at different times. Catholic countries (Spain, Portugal, Italy, Poland, Hungary, France) adopted within months of 1582. Protestant countries resisted: Germany adopted in 1700, Britain and the American colonies in 1752 (Wednesday 2 September 1752 was followed by Thursday 14 September 1752, prompting the ‘Calendar Riots’), Sweden in 1753, Japan in 1873, Russia in 1918 after the October Revolution, Greece in 1923, and Turkey in 1926. Saudi Arabia adopted only in 2016. The Russian Orthodox Church and several other Eastern Christian churches still use the Julian calendar for liturgical purposes - which is why Orthodox Christmas falls on 7 January rather than 25 December.

Year 2028 is the next leap year after the current common year 2026. It is preceded by leap years 2024, 2020, 2016, 2012, 2008, 2004, and 2000 (which was a leap year because 2000 is divisible by 400). It is followed by leap years 2032, 2036, 2040, 2044, 2048, 2052, 2056, 2060, 2064, and so on - one every four years until the next century-year exception in 2100 (which will NOT be a leap year because 2100 is divisible by 100 but not by 400).

Leap day, 29 February, is a special day. Approximately 5 million people worldwide were born on 29 February. They are colloquially called ‘leaplings’ or ‘leap-day babies’. Astrologically, leaplings are still Pisces (typical Pisces dates are 19 February to 20 March). The Honor Society of Leap Year Day Babies, founded in 1988, hosts global celebrations every four years. Famous leaplings include rapper Ja Rule (1976), motivational speaker Tony Robbins (1960), and astronaut Frederick Sturckow (1961).

Modern calendar software handles leap-year arithmetic via the standard library. JavaScript's Date object correctly identifies 29 February 2028 as a valid date. UNIX timestamp 1840147200 corresponds to 00:00:00 UTC on 29 February 2028 - a valid integer offset from the UNIX epoch. ISO 8601:2019 codifies the YYYY-MM-DD format and explicitly defines 29 February as a valid date only in leap years. PostgreSQL, MySQL, SQLite, Oracle, and SQL Server all enforce this.

Citation footnotes: the Gregorian calendar reform appears in the 1582 papal bull Inter gravissimas. The UK Calendar (New Style) Act 1750 codifies the British adoption. ISO 8601:2019 is the current international standard. The Honor Society of Leap Year Day Babies maintains leapyearday.com. NIST in Boulder, Colorado, and the US Naval Observatory in Washington DC monitor the tropical-year length via VLBI observations. The IANA Time Zone Database (TZDB) at iana.org/time-zones tracks calendar-rule changes since 1880.