I went to Nara while I was in Kyoto, and the journey itself took quite a while, so if you want to see everything in Nara, I advise you left a bit early.
From Osaka, it takes about 56 minutes to Nara.
From Kyoto, it takes about 69 minutes to Nara.
Nara is pretty big, and requires a lot of walking.
So prepare your legs and wear your most comfortable shoes before you head there!
.......... Actually, you should do this every time you go on a holiday. ^-^