Is making up the prayers missed over a lifetime restricted to particular times?

Question

In making up the prayers missed over one’s whole life, is it necessary to observe the [prayer] times?

Answer

This observance is not necessary; it is valid to perform, even at a single time, the qada’ of one day and one night — as much as one is able. However, the qada’ prayers should be performed in such a way that no one else comes to know that this is in fact qada’.

Source: Fatawa Mahmudiyya

Preview. The full text opens with JavaScript enabled.