Rabbi Eliezer and Rabbi Akiva were sitting in Bnei Barak. They were engaged in a Chavaya Pnimit of the Sippur of Yetsiat Mitsrayim, until the time of Kriyat Sh'ma of the morning. They were notified by their Talmidim, as they were sitting in a cave with no sunlight, hiding for the Romans, during the rebellion of Bar Kochba.
Rabbi Eliezer and Rabbi Akiva discussed Brit Bein HaBetarim, the decree of 400 years of slavery and actual suppression, a suppression they were themselves experiencing. Rabbi Eliezer said that it would last until 400 years from 3409, while not counting 104 years of Jewish independence, of the Chashmonayim. So the end of the suppression, in the view of Rabbi Eliezer, would be in the year 3913. Rabbi Akiva said that the 400 years were actually 500 years, just as 40 Makot were actually 50 Makot. Therefore, the end of the suppression would come in the year 3909.
Baruch HaMakom, Baruch Hu, who had a Machshava according to both Rabbi Eliezer and Rabbi Akiva. He did not count the 104 years of Jewish independence, following rabbi Eliezer. He counted till 500, as did rabbi Akiva. And He counted the whole night, until the time of Kriyat Sh'ma.
In His Machshava, 210 years were already finished in Galut Mitsrayim, and 70 years, of rabbi Elazar ben Azarya, in Galut Bavel. Remained in His Machshava only 220 years, starting in 3409. Because, unfortunately, the Chasmonayim missed the opportunity of 3629, vaYar Yisrael et haYad, right and left together, rabbi Akiva and rabbi Eliezer, two Hands were to be counted for every year, giving 2200 years. Plus the 104 years of the Chashmonayim, which leads us to 2304 years. Therefore, rabbi Akiva's 500 "years" were full in the year 5713, while 5708 was when 499.5 was reached. It was the year of the rise of Medinat Yisrael. Such was His Machshava.
Baruch SheNatan Torah l'Amo Yisrael, Baruch Hu.
Pesach Sameach!