“Muhammad ibn al-Faraj once wrote to al-‘Askariy (a.s.), asking about what is narrated, for calculating to fast, from his ancestors about the five days of the last year and six days of the coming year. He (the Imam) wrote, ‘It is correct but count five days in every four years and in the sixth year six days in between the first and the new. In those other than this it is five and five.’ Al- Sayyariy has said that this is because of al-Kabisah (calculating system). He has said that our people have calculated it and they found it to be correct.’ He (the narrator) has said that Muhammad ibn al- Faraj wrote to him (the Imam) in the year two hundred thirty eight about this calculation. (The answer said), ‘This calculation is not easy for everyone to follow. This is for those who know the years and that when al-Kabisah year was. Then crescent of the month of Ramadan of the first night is correct for them. Once the crescent of the night is established, then it is correct for them by the will of Allah.’”