Upvote:4
The reason for the confusion is that we don't know the exact dates. We have traditional dates, and we have reconstructions, but the latter can be disputed.
Per the Cambridge History of Japan, vol. 1:
But our knowledge of what was really occurring between the rule in the third century of Queen Himiko (reported in the Wei chih) and the reign from 592 to 628 of Empress Suiko (who reestablished relations with China) continued to be quite hazy and imprecise.
If you want the traditional dates, Gina Barnes in her Protohistoric Yamato (1988) has them listed, along with better estimates for their actual rule:
Regent | Traditional Dates | Adjusted/True Reign Dates |
---|---|---|
Keiko | 71–130 | 219–249 |
Seimu | 131–190 | 249–280 |
Chuai | 191–200 | 280–316 |
Jingo | 201–269 | 316–343 |
Ojin | 270–310 | 346–395 |
Nintoku | 313–399 | 395–427 |
The reason for this is just the time that had since elapsed and imperfect reconstructions by ancient (now to us) Japanese scholars, as Barnes notes (p.10):
The compilation of the materials that were later incorporated into these chronicles began during Emperor Keitai's reign in the early sixth century. This reflects on the historicity of the texts: the Nihon shoki's early sections are chronologically unreliable, but events recorded from the fifth century onward are thought to be fairly accurate; Philippi (1969: 5) reports also that it "has often been suggested that the 'now' of the Kojiki refers to this period" under Emperor Keitai.
(Emphases mine.)