What is the Opportune Time To Buy Stocks?

Every time, there is an economic depression, specifically something like the present global slump, which is the second biggest in the century, people are going to lose all sense of reality and confidence and claim that depressed markets are not the right time to enter them. I would beg to differ. I understand that recessionary markets require a lot of guts and very deep pockets but at the same time, I would also like to state that when stocks are at multi-year lows, it is the time to enter right away. I know there is risk but with intelligent planning, the risks are reduced and the rewards really multiply.