Anytime! Just kidding — leggings are not preferred or appropriate for every situation, though that does seem to be changing as loungewear is getting fancier and slacks are getting more comfortable.
Leggings are a perfect option for most activities where you’d normally wear shorts or hiking pants — think cycling, yoga, running, and backpacking. The specific legging might vary for each activity (see below for needs like durability and pockets), but overall, leggings are a comfortable option for most active and non-active outings.