Time based buying is not necessary, instead it should be dip based or support based on chart where price bounce back is likely to happen. Dollar-cost averaging is the strategy of spreading out your stock or fund purchases, buying at regular intervals and in roughly equal amounts. When done properly, it can have significant benefits for your portfolio. this strategy will make your into quickly when market bounces back that is why  it is considered very successful strategy.

 https://www.nerdwallet.com/article/investing/dollar-cost-averaging-2