millennial

from WordNet (r) 3.0 (2006)

millennial
    adj 1: relating to a millennium or span of a thousand years
           [syn: {millennial}, {millennian}]

from The Collaborative International Dictionary of English v.0.48

Millennial \Mil*len"ni*al\, a.
   Of or pertaining to the millennium, or to a thousand years;
   as, a millennial period; millennial happiness.
   [1913 Webster]