What is the age limit in years between the Salaf and the Khalaf?

The Salaf are the people of the three virtuous generations whom the Prophet, peace and blessings be upon him, praised. These are the Companions, the Tabi'in (successors), and their successors. Ibn 'Uthaymeen defines the Salaf by a methodology that includes everyone who adheres to what is indicated by the Qur'an and Sunnah, and by a temporal limit that includes the three favored generations. Shaykh al-Islam Ibn Taymiyyah holds that the consideration for the three generations is based on the passing away of the majority of the people of each generation. He states that the three generations concluded with the end of the caliphate of the four Rightly Guided Caliphs for the majority of the Companions, and in the late era of the younger Companions for the majority of the Tabi'in, and in the late Umayyad and early Abbasid periods for the majority of the followers of the Tabi'in. Some scholars believe that the time of the three favored generations ends around the year 220 AH. It is incumbent upon a Muslim to adhere to what the people of these virtuous generations were upon in terms of creed, worship, and conduct.