Finding the time to do things that you want to and need to do, can be one of the hardest things we have to plan around. A busy job and long hours don't really help us either, if you want to exercise, if you want to get fit and if you want to start leading a healthy lifestyle then "I don't have time to exercise" is just not good enough. It's essentially a decision already made up, the statement implies you have little intention to try or plan to exercise. The truth is the things in life we do, we do because we want to do them and therefore have MADE time to do them. If you want to do something, you need to make the time to do it.
I like to quote Henry Ford in this sort of situation with the quote
"whenever you think you can or when you think you can, you're right"
Stop thinking with the "I don't" " I can't" and start think with the "I will" " I can" and you will soon be finding time to exercise.
Exercise after all gives us more energy, makes us more productive releasing feel good endorphins, not to mention the physical and health benefits.
I often here people saying they only have 10 minutes, so they can't do anything. 10 minutes is perfect, get down and do a little core workout or take the time to do some full body stretching, in your lunch break, before or after work. You don't need to join a gym either, depending on your fitness level start going for a short walk or run, slowly increase it, if your only out for 15 minutes then it's a start and more importantly your doing something.