How does a prisoner pray in a dark underground cell, while shackled, and unaware of prayer times or the start of Ramadan?

Prayer and fasting are not waived for prisoners or captives. They must endeavor to ascertain the correct times for these acts of worship. If they have a strong presumption that the time for prayer has begun, they should pray. If they have a strong presumption that the time for fasting has begun, they should fast. If they strive and investigate to the best of their ability, their acts of worship are valid and sufficient, whether it is later revealed that they performed them at the correct time, after the correct time, or if nothing is revealed to them.

If it becomes known that he fasted on the days of Eid, he must make up those fasts. However, if it becomes known that he prayed or fasted before the correct time, he must repeat the prayer and fasting.

If the months become confused for him regarding fasting, his obligation to fast is not waived. If he strives and fasts, there are five possible scenarios: 1. Continued ambiguity: His fast is sufficient, and he does not need to repeat it. 2. His fast coincides with Ramadan: It is sufficient for him. 3. His fast coincides with the period after Ramadan: It is sufficient for him, according to the majority of jurists. 4. His fast coincides with the period before Ramadan: - If it becomes clear before Ramadan arrives: He is obligated to fast Ramadan when it comes. - If it becomes clear after Ramadan has passed: It is not sufficient for him, and he must make it up (the view of the Maliki and Hanbali schools, and the relied-upon opinion among the Shafi'is), or it is sufficient for him (the view of some Shafi'is). 5. His fast coincides with part of Ramadan but not another part: What coincided with Ramadan or after it is sufficient for him, but what coincided before it is not sufficient for him.