What is the ruling on fasting on Eid al-Fitr, and is there a sin upon one who fasts for 29 days while the country in which he fasted relies on astronomical رؤية (sighting) and announces Eid more than 10 days late?

The month is established by one of two matters: sighting with the naked eye, or completing the previous month as thirty days, based on the saying of the Prophet, peace be upon him: "Fast when you see it [the crescent moon] and break your fast when you see it. If it is obscured from you, then complete the number of Sha'ban as thirty days." Astronomical calculation does not establish the crescent moon legally according to the majority of scholars, and it is not permissible to follow a country that relies on it if its weakness is known. Whoever obeyed a country that relied on astronomical calculation out of ignorance bears no sin, nor does he sin by fasting on the day of Eid according to astronomical calculation if it does not conform to a legal sighting. Whoever fasted twenty-nine days based on astronomical calculation, and it became clear that it was twenty-eight days by legal sighting, must make up one day if Ramadan was twenty-nine days, and two days if it became clear that it was thirty.