Is it permissible to set a date for repentance, such as saying, "I will repent next Thursday"?

Repentance from sins must be initiated immediately; it is not permissible to delay it. Indeed, delaying repentance is a sin that necessitates repentance. And whoever delays repentance has erred twice: by committing the sin, and by delaying repentance. No one is guaranteed to live until tomorrow, for death comes suddenly to the healthy and the sick, the young and the old. Allah Almighty said: "Indeed, Allah [alone] has knowledge of the Hour and sends down the rain and knows what is in the wombs. And no soul perceives what it will earn tomorrow, and no soul perceives in what land it will die. Indeed, Allah is Knowing and Acquainted."