Zimri became king in Asa's 27th year, and he was king only seven days. Why did Amri become king only in Asa's 31st year?
Rashi: For five 1 years there was opposition of Tivni. In Asa's 31st year, he ruled totally.
There were only four years in between! Refer to 16:23:2:1*. Radak cites Seder Olam to say four months. Kli Yakar says that this is a mistake; it should say four years. Our text of Seder Olam says 40 years; surely it should say 'four'. (PF)
Amri become king in Asa's 31st year, and reigned for 12 years. How did his son Achav become king in Asa's 38th year (verse 29)?
Rashi: He reigned 12 years in all, including five 1 years with opposition. He ruled totally for seven years, starting in Asa's 31st year.
Kli Yakar: Rashi counts partial years (the 27th and 31st of Asa) as full years.
Why did he reign for six years in Tirtzah?
Rashi: That was before he built Shomron.
Radak: Until then there was opposition of Tivni 1 . Afterwards, he ruled totally seven years. His 13th year 2 is not counted, for it was not complete.
How can he explain why it says that Amri become king in Asa's 31st year? He cannot say [like Rashi] that this is when he ruled totally, for Zimri became king in Asa's 27th year. Even if partial years are counted like full years, we cannot count six years of disputed kingship! (PF) Kli Yakar - even after Tivni died, his supporters resented Amri. (His kingship was total only two years later.)
How can he say that there was even part of a 13th year? Even if we count Asa's 27th and 38th years as full years for Amri, he had only 12 years! (PF)