There’s no one-size-fits all answer to this question. For example, if you’re training for a marathon or other endurance events where speed is less important than the distance covered, then it doesn’t matter when you perform cardio. If however, your goal is to get leaner and stronger while increasing aerobic capacity (i.e., “cardio” in the classic sense), then your best bet would be to do cardio at least three times per week with each session lasting about 30 minutes.
I’m sorry but what does that even mean? It means that I don’t think there are really any good reasons not to do some form of cardiovascular exercise between 60% and 90% intensity every single day regardless of your goals or preferences; this includes people who generally avoid doing anything resembling “exercise”. The point here isn’t how much time you spend working out, but rather how intensely (and consistently) you work out each day; if none of these sentences make sense yet, perhaps it’s because they shouldn’t. 🙂