What is the ruling on differences arising among members of the same household regarding prayer times, and the times for abstaining from food (imsak) and breaking the fast (iftar)?

The prayer times must be known by the sharee'ah signs. Calendars can be used for reference but should not be relied upon entirely, unless they are based on observations of those sharee'ah signs and have been approved by trustworthy scholars. If calendars differ and it is difficult to determine the time based on the sharee'ah signs, the prayer should not be performed until there is certainty or strong presumption that the time has begun. Similarly, a fasting person should not eat or drink until they are certain or have a strong presumption that the time for Fajr has begun. They may, however, abstain as a precaution at the earliest time indicated in those calendars.