If you know that ankles and calves are the problem, I personally would just spend some time hitting them specifically as opposed to trying to fit yoga into your schedule. For me, trying to fit one more thing in my already cramped schedule is near to impossible.
I try to stretch my ankles and calves every other hour during the workday. So that's roughly five 2-3 minute stretch sessions during the workday.
Ankle circles, straight leg calves stretching, bent leg calves stretching, getting into your rock bottom squat position and push yourself deep in the hole stretching the hips and while your down there push down on the tops of your knees to hit the ankles again. I don't necessarily hit all of these each session.
You don't need to spend a lot of time at each session if you're doing frequently and after 2-3 weeks you'll notice a huge improvement in your flexibility.