In this paper I shall examine the philosophical cosmology of medieval Jewish thinkers as developed against the backdrop of their views on time and creation. I shall concentrate upon the Neoplatonic and Aristotelian traditions, with a particular eye to the interweaving of astronomy, cosmology and temporality. This interweaving occurs in part because of the influence of Greek cosmological and astronomical texts upon Jewish philosophers. The tension between astronomy and cosmology is best seen in Maimonides' discussion of creation. Gersonides, on the other hand, is more willing to incorporate astronomical material into his cosmological thinking. By examining these motifs, we shall arrive at a greater understanding of the dimension of temporality within Jewish philosophy.