The "Great Sign" of Rev 12 was day 266 .... Guess What...
On the Gregorian Calendar day 266 is Sept. 23 and the Great Sign in the Heavens of Rev 12 was Sept. 23, 2017.
On the Enoch calendar (364 days) which begins on Nisan 1 (or March 22 this year) day 266 will fall on Dec. 12 , 2019. That is 24 Kislev on the Enoch calendar , the 24th day of the 9th Hebrew month --- the day Haggai says will be a "blessing"... Haggai 2:10 . So one might say Dec 12th , 2019 is two years from the Great Sign in the Heavens of Sept 23, 2017 and does so using both the Gentile and Hebrew calendars....
I am not familiar with the Enoch calendar. The link below has a detailed explanation.