Yes, 2000 was a leap year. Since 1752, in this country, years exactly divisible by 100 are only leap years when they are also exactly divisible by 400. So 1800 and 1900 were not leap years, neither will 2100 or 2200 be leap years. The correction to the Julian Calendar then in use was made by Act of Parliament 24 George II (1751) c.23 to align the calendar with that 'generally practised by almost all other Nations of Europe'. This (Gregorian) calendar was published by Pope Gregory XIII as a Papal Bull "Inter Gravissimus" in 1582, but it took some time for its use to become established. The change was made to avoid the gradual drift of the seasons, notably the Vernal Equinox on which the date of Easter depended, earlier in the year.