not young

aged ancient decrepit elderly gray mature tired venerable

fossil senior versed veteran

along in years broken down debilitated enfeebled exhausted experienced geriatric getting on gray-haired grizzled hoary impaired inactive infirm matured olden oldish over the hill past one's prime seasoned senile skilled superannuated wasted

new young youthful

green inexperienced

contemporary current fresh late modern recent up-to-date