1667 - 5 Sep. 1747, you are correct sir.
Although I find the reference to 1688 hard to accept being he was only 21 at the time. Forging that level of quality at 21, possible yes but I doubt it. Its a really nice blade to my eyes.
An extract from Roger R's book states
The Yondai received the title ‘Ômi Daijô’ on 10 March 1700 and subsequently changed his mei to “Hizen Kuni Jû
Ômi Daijô Fujiwara Tadayoshi”; he also signed “Tadayoshi Saku” as did the Shodai. Some time after 1709 he began
signing “Ômi Daijô Fujiwara Tadayoshi”, perhaps copying his grandfather’s later technique of simply signing “Ômi
Daijô Fujiwara Tadahiro”. He is the only Tadayoshi to use ‘Ômi Daijô’ in his Tadayoshi mei, and he therefore became
known as ‘Ômi Daijô Tadayoshi’, however there are also dai-mei by the 5th gen. signing ‘Ômi Daijô Fujiwara
Tadayoshi’, as we shall see.
That does not support the 1688 claim in my limited opinion.
Full credit to Roger for his research referenced here