There are 571 years between the Prophet Jesus (as) and the Prophet Muhammad (saas), Ulu al-'azm Prophets (the Resolute Messengers), and Hazrat Mahdi (as) will come some 400 years after Imam Rabbani

Some people think that the fact that Hazrat Mahdi (as) will come some
400 years after Imam Rabbani will somehow diminish the worth of Imam
Rabbani and claim that Hazrat Mahdi (as) will come 1000 years after
the imam. The fact is, however, that Hazrat Mahdi's (as) coming around
400 years after Imam Rabbani in no waydiminishes his value. Allah sent
our Prophet (saas) just 571 years after the Prophet Jesus (as), a
Resolute Messenger. The Prophet Muhammad (saas) came soon after the
Prophet Jesus (as), with a new law and book. In other words, there are
571 years between the two Resolute Messengers. Hazrat Mahdi (as) will
come some 400 years after Imam Rabbani. Indeed, Imam Rabbani declared
as such himself,saying that Hazrat Mahdi(as) will come 1000 yearsafter
the death of our Prophet (saas):
The end of this Ummah will begin WITH THE BEGINNING OF THE
SECONDTHOUSAND. IN OTHER WORDS, AFTER THE DEATH OF RASULULLAH... The
full implementation of the moral values of the Qur'an and the renewal
of the Islamic world IS INTHIS SECOND THOUSAND. THE JUST WITNESSES OF
THE TRUTHFULNESS OF THIS CASE ARE THE EXISTENCE OF JESUS (AS) AND THE
MAHDI (AS) IN THIS MILLENNIUM (IN OTHER WORDS, IN THE THOUSAND YEARS
FOLLOWING THE DEATH OF OUR PROPHET (SAAS)). (Imam Rabbani, Letters of
Rabbani, p. 261)
Here, Imam Rabbani is clearly and explicitly speaking of NOT AFTER HIS
OWN DEATH, BUT AFTER THAT OF OUR PROPHET (SAAS).
As Imam Rabbani says, the end of the Islamic world will begin with the
second millennium and Imam Rabbani, the Prophet Jesus (as) and Hazrat
Mahdi (as) will be in the second millennium after the death of our
Prophet (saas).