Reference for Rosh Hashanah 4:8

ויציאת מצרים גופה מנלן דמניסן מנינן דילמא מתשרי מנינן

Here Solomon's reign is put side by side with the exodus from Egypt,<span class="x" onmousemove="('comment',' I.e., the event recorded is dated by both of them.');">⁸</span> [to indicate that] just as [the years from] the exodus from Egypt are reckoned from Nisan, so [the years of] Solomon's reign commenced with Nisan. But how do we know that the years from the exodus from Egypt itself are reckoned as commencing with Nisan?

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