What is the ruling on someone who traveled a long distance in the last days of Ramadan and committed fornication upon arrival, thinking it was not Ramadan, then it became clear that he had missed two days of fasting in Ramadan?

The default is the continuation of the month of Ramadan and the non-confirmation of the crescent of Shawwal. It is not permissible to exit it except with certainty. Committing the crime of adultery is a grave sin and a major offense. The perpetrator of adultery must repent, seek much forgiveness, and ask for pardon from Allah.

If the travel was for a sinful purpose, or if there was an intention to reside in that country for four days, excluding the days of entry and exit, and his breaking of the fast was due to intercourse, then expiation and making up the fast are obligatory upon him. The expiation is fasting for two consecutive months, and if he is unable to do so, then feeding sixty poor people. However, if the travel was for an obedient purpose and he did not intend to reside, but rather intended to return to his country after accomplishing his objective, then he is permitted the concessions of travel, including breaking the fast. Expiation is not obligatory upon him; rather, he only needs to make up the fast, along with repenting to Allah Almighty for this great sin.