Source : Webster's Revised Unabridged Dictionary (1913)

Untimeliness \Un*time"li*ness\, n.
   Unseasonableness.

Source : WordNet®

untimeliness
     n 1: being at an inappropriate time [syn: {unseasonableness}]
          [ant: {seasonableness}, {seasonableness}]
     2: the quality of occurring at an inconvenient time [syn: {inopportuneness}]
        [ant: {opportuneness}]