Pirkei D'Rebbi Eliezer on Sod HaIbbur

Chapter 8 of Pirkei D'Rebbi Eliezer brings a history of Sod HaIbbur (Sod HaIbbur meaning the secrets behind the calendar. On a base level, this means when to add a leap month.).

First Hashem took care of Sod HaIbbur. Then He passed it on to Adam HaRishon in Gan Eden (Which is problematic if we are to say that there were no years before Adam HaRishon's stay in Gan Eden).

• Adam passed on the knowledge to Chanoch.
• Chanoch passed on the knowledge to Noach.
• Noach passed on the knowledge to Shem.
• Shem passed on the knowledge to Avraham Avinu.
• Avraham Avinu passed on the knowledge to Yitzchak Avinu.
• Yitzchak Avinu passed on the knowledge to Yaakov Avinu.
• During Yaakov Avinu's stay outside of Eretz Yisrael, Yitzchak resumed the adding of the leap months.
• Yaakov Avinu passed on the knowledge to Yosef, and Yosef was the one that added the leap months in Mitzraim.
• When Yosef and his brothers passed away, the leap months became lessened "נתמעטו העיבורין מישראל", until the time that Hashem gave the mitzvah to sanctify the months to Moshe and Aharon.

It goes on to say there that just as during Galus Mitzraim, the leap months became lessened, so to it will be towards the time of the end of the servitude to the Fourth Kingdom, until the coming of Moshiach.

And just like Hashem was revealed to Moshe and Aharon to bring Sod HaIbbur back to Am Yisrael, thus too Hashem will be revealed in the future to bring it back to us.