The whole idea of Moshiach’s coming is that we don’t know the date.
Achakeh lo b’chol yom sheyavo
We do know when he will definitely will have come, and that’s by the year 6000, or 2240 CE.
There is a famous contradiction in Chazal: On one hand there are many stories that state that Moshiach can come any day (Hayom im bko’lo tishma’u). For instance the famous Gemara that if all of Klal Yisroel keep two Shabbosim Moshiach will come immediately, or all do t’shuvah.
On the other hand there are multiple references to a specific preordained date (Chisheiv es hakeitz).
There are other contradictions, such as whether Moshiach will be with or without miracles, and if there will be a terrible gzeira or not.
Nu?
The answer is that there actually are two dates, B’Kitzo and Achishena.
If everyone does Teshuvah and merits the geula, it will happen miraculously and before its preordained time. This is Achishena
If nobody changes by the preset time (the keitz) Hashem will “…Bring a king (leader) upon them whose gezeiros are as difficult as Haman’s”, to quote the Gemara in Sanhedrin, and everyone will be forced to do Teshuvah to save themselves, out of fear!
For a more in depth discussion see the Sefer “Otzar Acharis HaYamim”.
(And yes, it has a haskama from R’ Chaim Kanievsky)