Source : Webster's Revised Unabridged Dictionary (1913)

Timeliness \Time"li*ness\, n.
   The quality or state of being timely; seasonableness;
   opportuneness.

Source : WordNet®

timeliness
     n 1: being at the right time [syn: {seasonableness}] [ant: {unseasonableness},
           {unseasonableness}]
     2: timely convenience [syn: {opportuneness}, {patness}] [ant: {inopportuneness}]