2. I have counted with right ascension 0º at March 21 (day number 80 in the Gregorian calendar).
"Right ascension (abbreviated RA; symbol α) is the angular distance measured eastward along the celestial equator from the vernal equinox to the hour circle of the point in question ... In astronomy, the hour circle of a celestial object is the great circle through the object and the celestial poles. It is perpendicular to the celestial equator. In other words, it is analogous to meridians or longitudes on a globe." (Wikipedia)
The Gregorian calendar is not perfect and vernal equinox (north of the equator) often occurs in March 20, in spite of the decree of the Catholic Church that it will always be on March 21:
"The Christian churches calculate Easter as the first Sunday after the first full moon on or after the March equinox. The official church definition for the equinox is March 21; however, as the Eastern Orthodox Churches use the older Julian calendar, while the Western Churches use the Gregorian calendar, both of which designate March 21 as the equinox, the actual date of Easter differs." (Wikipedia) I have assumed also the G text displays the right ascension positions of the stars counted from March 21 in order to have the desired stability. In my star list Aldebaran is at RA 69.2 and Antares at RA 250.1 and these numbers are based on 04h 33m respectively on 16h 26m (data which I have fetched from my astronomy book, printed in 1977). Assuming these numbers refer to an epoch defined for 1950 it should be suitable to reduce the day numbers with 1 in order to compensate for the precession from around 1870:
Alluding to the idea of the birth of the summer year implied in March 21, I have put a little star (*) to indicate the number of right ascension days from the northern spring equinox. With March 21 as day 80 it is easy to add 80 to the right ascension days in order to find the day numbers and then to translate these to my suggested Gregorian dates. E.g. was around 1870 the Gregorian day number for Aldebaran 80 + 68 = 148 which means May 28:
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