The Collaborative International Dictionary
Cotemporaneousness
Cotemporaneous \Co*tem`po*ra"ne*ous\ (k?-t?m`p?-r?"n?-?s), a. Living or being at the same time; contemporaneous. -- Co*tem`po*ra"ne*ous*ly, adv. -- Co*tem`po*ra"ne*ous*ness, n.
Wiktionary
cotemporaneousness
n. Quality of being cotemporaneous; existence or occurrence in the same time period.