So in case anybody is curious about the claim that October 23 is too late, I updated the Wikipedia page listing the past debates to include the date.

https://en.wikipedia.org/wiki/United_States_presidential_debates

In general, the first debate takes place in late September or early October, and the final debate occurs in mid to late October with two or three debates being the norm. The first debate occurring in June is new this year as the debates normally start after the nominations are complete.

So, unsurprisingly, Trump’s argument has no historical basis and complaining that the debate is too close to the election is nonsense.