In his work The Letters of Rabbani, the great Sunni scholar Imam Rabbani gives two important conditions regarding the coming of Hazrat Mahdi (as).
The first of these conditions is that Hazrat Mahdi (as) will appear one thousand years after our Prophet (saas).
This is revealed on page 1/569 of his Letters of Rabbani:
However, what is anticipated is this; the renewal of this concealed state AFTER ONE THOUSAND YEARS HAVE PASSED. His being given superiority, finding water and increase... The original of such virtues (perfections) will appear and cover its abasement… AND LET HAZRAT MAHDI (AS) who values devotion to might COME. May Allah be pleased with him.
(Letters of Rabbani, 1/569)
We are now in the year 1430 (Islamic calendar). This date shows that 1000 years have passed since our Prophet (saas). It also proves that the first of Imam Rabbani’s conditions necessary for the appearance of Hazrat Mahdi (as) has come about.
According to his Companions, the Messenger of Allah (saas) said:
"When Abbasi Malik arrives at Khorasan, one of the signs of the coming of the promised Mahdi, A DOUBLE-TOOTHED (1) LIGHT SHEDDING (2) HORN (3) WILL APPEAR IN THE EAST."
"A TAILED STAR (COMET) WILL BE BORN IN THE EAST AND SHED ITS LIGHT."
That comet has been born. But is it that one, or another similar one?
-That this star is called a comet is probably based on the following:
-The course of the constant IS FROM WEST TO EAST (4)...
The situation of this star follows this course. In other words, its head faces east and its tail faces west. The long white part is in its rear. Therefore:
-It is appropriate for it to be described as having a tail.
ITS DAILY PASSAGE, ON THE OTHER HAND, IS FROM EAST TO WEST. (5)...
Allah best knows the truth.
(1) ... double-toothed...:
The fact that the tail of the comet Lulin is forked completely matches the term double-toothed in the hadith.
(2) ... light-shedding...:
The term light-shedding in the hadith refers to the brightness of the comet Lulin, which exceeded that of six stars as it approached the Earth.
(3) ... a horn...:
The main distinguishing feature between Lulin and other comets is that as well as the comet having a tail in the rear of its body, it also has a tail in the front. Examination of photographs of Lulin and its two tails immediately put one in mind of a horn.
(4) The course of the constant is from west to east...:
The hadith goes on to say that “The course of the constant is from west to east...“ This refers to the movement of heavenly bodies, which information is in full agreement with the astronomical findings of the 20th century. Indeed, all heavenly bodies travel from WEST to EAST.
(5) Its daily passage, on the other hand, is from east to west. ...: Here the expression “Its daily passage, on the other hand, ...” indicates that the comet Lulin, as opposed to all other heavenly bodies, travel from east to west.
The reference to a “double-toothed, light shedding” horn, cited in the hadith of our Prophet (saas) as a portent of the appearance of Hazrat Mahdi (as) whose coming is anticipated in the End Times, and described in detail by Imam Rabbani, indicated the comet Lulin, which passed closest to the Earth on 24 February, 2009, that is the year 1430 according to Islamic calendar.
Another highly significant feature of this comet is that scientists say that it will next pass by the Earth after at least another 1000 years.
(Web sites confirming that the comet Lulin passes by once every thousand years and that its next passage will be in a thousand years’ time.)
It is narrated from Anas Malik that Rasulullah (saas) said:
THE LIFE SPAN OF THE WORLD IS SEVEN DAYS IN THE DAYS OF THE HEREAFTER. Almighty Allah says: One day in the sight of your Lord is like one thousand of your years.
It is narrated from Anas Ibn Malik that Rasulullah (saas) said:” Whoever meets the needs of his brother in the religion on the path of Allah, Allah WILL GIVE HIM MERIT OF THE SEVEN THOUSAND-YEAR LIFE SPAN OF THIS WORLD, as if he had fasted in the days and spent the nights in prayer.”
(Al-Burhan fi Alamat al-Mahdi Akhir al-Zaman, p. 88)
Ahmad Ibn Hanbal relates;
FIVE THOUSAND SIX HUNDRED YEARS HAVE PASSED FROM THIS WORLD.
(Al-Burhan fi Alamat al-Mahdi Akhir al-Zaman, 89)