Passage: Since the 1980s and 1990s, the Magachs have been gradually replaced by Merkava tanks as Israel's front-line main battle tank. However, a large majority of the IDF's armored corps continued to consist of Magach variants until the 1990s, and the tank was continuously upgraded during this time.

Question: Since what era's did the Magchs gradually been replaced for Merkava tanks?
1980s and 1990s