The Collaborative International Dictionary of English v.0.48:

Earliness \Ear"li*ness\, n.
   The state of being early or forward; promptness.
   [1913 Webster]

WordNet (r) 3.0 (2006):

earliness
    n 1: quality of coming early or earlier in time [ant:
         lateness]

Moby Thesaurus II by Grady Ward, 1.0:

28 Moby Thesaurus words for "earliness":
   anachronism, antecedence, antecedency, antedate, antedating,
   anteriority, anticipation, earlier state, historical error,
   lateness, metachronism, misdate, misdating, mistiming,
   parachronism, past time, postdating, precedence, precedency,
   precession, predating, preexistence, priority, prochronism,
   prolepsis, status quo ante, tardiness, unpunctuality