A millennium (plural millennia or millenniums) is a period equal to
Sometimes, it is used specifically for periods of a thousand years that begin at the starting point (initial reference point) of the calendar in consideration (typically the year "1"), or in later years that are whole number multiples of a thousand years after it. The term can also refer to an interval of time beginning on any date. Frequently in the latter case (and sometimes also in the former) it may have religious or theological implications (see
There are two methods of counting years: current years (the count begins at the
The original method of counting years was
The main issues arise from the content of the various year ranges. Similar issues affect the contents of centuries. Decades are not subject to ambiguity, as they are named according to their leading numbers: for example, the decade called "the 1990s" by its naming does not include 2000.
For those following ordinal year names:
For those who are influenced by the leading digit: