The G Calendar is the wrong calendar for Jesus’s day, He went by the Lunar
Don’t know what you are trying to say about Mark 13?
Genesis 1:14 And God said, Let there be lights in the firmament of the heaven to divide the day from the night; and let them be for signs, and for seasons, and for days, and years:
Lunar, lunar-solar, solar, sidereal (in Hebrew lit. 'year of the stars')... they all serve together as signs.
Mark 13 was linked to the instruction to watch, because that is the word from which the Gregorian calendar is derived, the one some don't think is important to watch because it is "wrong".
The Gregorian calendar is internationally the most widely used civil calendar.[1][2][Note 1] It is named after Pope Gregory XIII, who introduced it in October 1582.
It was a refinement to the Julian calendar[3] involving an approximately 0.002% correction in the length of the calendar year. The motivation for the reform was to stop the drift of the calendar with respect to the equinoxes and solstices—particularly the northern vernal equinox, which helps set the date for Easter. Transition to the Gregorian calendar would restore the holiday to the time of the year in which it was celebrated when introduced by the early Church. The reform was adopted initially by the Catholic countries of Europe.
Gregorian Calendar