1) Coetaneous 2) Contemporaneous 3) Contemporary 4) Equally old 5) Of the same age 6) Of the same period 7) Synchronal 8) Synchronic 9) Synchronous 1) Coetaneous 2) Synchronal 3) Synchronic 4) Synchronous 
of the same length of time; having the same duration
• (n.) One of the same age; a contemporary. • (n.) Of the same age; existing during the same period of time, especially time long and remote; -- usually followed by with.
Co·e'val adjective [ Latin coaevus ; co- + aevum lifetime, age. See Age , noun ] Of the same age; existing during the same period of time, especially time long and remote; -- usually followed by with . « Silence! coeval with et...Co·e'val noun One of the same age; a contemporary. « As if it were not enough to have outdone all your coevals in wit. Pope. » 
of the same period coexisting 
Coeval: Of the same or equal age or duration. For example, the two elderly men were coeval with one another. Coeval usually refers to coexistence for a very long time. 'Coeval' comes from the Latin 'coaevus' meaning 'of the same age.' 'Coaevus' is derived from the prefix 'co-'('in or to the same degree') and 'aevum' ('age' or 'lifetime'). The root ...
coeval, coaeval 1. Originating or existing during the same period; lasting through the same era. 2. Someone of the same era or period; a contemporary.
of the same age, date, or duration; equally old: Analysis has proved that this manuscript is coeval with that one. · coincident: Leonardo da Vinci and Michelangelo were only approximately coeval.
of the same period