A millennium is a period of time equal to one thousand years (1,000)—from the Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 phrase , thousand, and , year—often but not necessarily related numerically to a particular dating system
A calendar is a system of organizing days for social, religious, commercial, or administrative purposes. This is done by giving names to periods of time, typically days, weeks, months, and years. The name given to each day is known as a date. Periods in a calendar are usually, though not...


For example, a millennium could start at the beginning of the year 289 and finish at the beginning of the year 1289.

Sometimes, it is used specifically for periods of one thousand years that begin at the starting point (initial reference point) of the calendar in consideration (typically the year "1"), or in later years which are whole number multiples of a thousand years after it.