The 24th century refers to the 100‑year span beginning on 1 January 2301 and ending on 31 December 2400 in the Gregorian calendar. Because centuries are counted ordinally, the first century covered years 1–100, so the 24th century covers the years commonly written as 2301 through 2400. The closing year, 2400, is notable under current civil calendar rules.
Calendar and leap‑year rules
Under the Gregorian calendar in widespread civil use, most years divisible by 4 are leap years. Years divisible by 100 are not leap years unless they are also divisible by 400. As a result, the year 2400 qualifies as a leap year because it is divisible by 400, making it a "century leap year." The next century leap year after 2000 is therefore 2400. For further reference on the rule, see Gregorian leap year rule.
Usage and common confusions
People sometimes confuse the 24th century with the 2300s; the latter phrase can mean the set of years 2300–2399. Strict century numbering places 2300 in the 23rd century and 2400 in the 24th. Similar confusions occur around millennial boundaries (for example, whether the 21st century began in 2000 or 2001).
Cultural and speculative references
The 24th century is a popular setting in science fiction and futurist speculation, used as a convenient near‑distant future for imagining technological, social, and spacefaring developments. Well‑known fictional universes place key events and characters in parts of the 24th century, which helps anchor stories in a plausible yet imaginative future era.
Notable distinctions and context
- Starts: 1 January 2301 (Gregorian).
- Ends: 31 December 2400 (Gregorian).
- Contains the century leap year 2400 under current leap‑year rules.
When discussing centuries, it is useful to state explicit year ranges to avoid ambiguity. The 24th century will be treated in calendars and historical timelines according to the conventions described above unless civil calendar systems are revised in the future.