These forms of the verb are known as gerunds. They’re declined in the same manner like those adjectives ending in -us, -um, -a, and they’re actually considered verbal adjectives.
Nunc non est tempus dormiendi et ludendi sed laborandi.
kembreg - That line is taken almost verbatim from Horace nunc tempus bibendi “now is the time of drinking”. They’re both correct. I’m not sure if there’s a fancy term for it, and perseus is down so I can’t check if it’s something to do with tempus, but you see this often. ad + accusative is normal in prose, genitive can be normal in poetry. Circumstance often dictates the choice. When the tools are back up, I’ll check it out for you.
we can also use the infinitive with TEMPUS and perhaps with other expressions of time. In a dialog by Cordieri (maybe that is not the exact spelling) that I got from the site where all the humanistic Colloquia are stored I read something like.
Visne ludere amice? Ita, amice, attamen non est tempus ludere.
Licet conjunctivo uti? Non est tempus ut ludamus! vos oro ut me certiorem faciatis.
Smily courtesy meae filae septorum annorum