What is the ruling on relying on Islamic internet applications and websites to determine prayer times and Imsak (such as sunset and sunrise) in non-Islamic countries?

"Prayer is not valid unless one knows that the time for it has begun, or has a strong presumption that it has. One can inquire about prayer times from Islamic centers, while also using applications for reference. It is not permissible to rely entirely on applications if the entity that prepared them is unknown, or if they are not based on a known source or a reliable calendar."