"When Julius Caesar established his calendar in 45 BC he set March 25 as the spring equinox. Since a Julian year (365.25 days) is slightly longer than an actual year the calendar drifted with respect to the equinox, such that the equinox was occurring on about 21 March in AD 300 and by AD 1500 it had reached 11 March. This drift induced Pope Gregory XIII to create a modern Gregorian calendar. The Pope wanted to restore the edicts concerning the date of Easter of the Council of Nicaea of AD 325." (Wikipedia)

My convention with a little star (*) before a number indicates the number of days from 'March 21, the date I have chosen to correlate with right ascension zero for the time I assume the text was created:


Ga1-1	Ga1-2	Ga1-3	*Ga1-4 (68)**	Ga1-5	Ga1-6
	Ain, θ¹ Tauri, θ² Tauri (65.7)		Aldebaran (68.2)	Theemin (68.5)
'May 25	'26	'27	'28	'29	'30 (150)
Sheratan 9	10	11	12	13	14

Possibly spring equinox according to the Julian calendar motivated 'May 25 as the date for the first glyph on side a; 325 (= 13 * 25) can be used as a reference to March 25 (because March is the 3rd month) and similarly May 25 can then be alluded to by 525 (= 21 * 25). The council of Nicaea took place in AD 325.

The manzil station Sheratan has 14 days instead of the normal 13. This probably indicates the insertion of an extra day for the 'birth' of the new year and possibly the extra day corresponds to 'May 30 and Ga1-6. The design of Ga1-6 makes clear there are 2 entities, one at the back side (the past) and one in front (ahead).

The manzil Pleione has its name from 28 Tauri (Pleione), the last star ('tail') of the Pleiades. Although it rises together with (only a few seconds later than) Atlas (27 Tauri):

At my assumed year for G (1870 A.D.) the stars Pleione and Atlas rose together heliacally in 'May 16 (in day 136 counted from 'January 1). This is the day before Sheratan 1, the first date of the manzil calendar.


Ga1-7	Ga1-8	Ga1-9	Ga1-10	*Ga1-11 (75)**
			Hassaleh (73.6)	Almaaz (74.7), Haedus I (74.8)
'May 31	'June 1	'2	'3	'4
Pleione 1 (15)	2	3	4	5


Ga1-12	Ga1-13	Ga1-14
Haedus II (75.9), ε Leporis (76.0), Cursa (76.4)	λ Eridani (76.7)	μ Leporis (77.6), ĸ Leporis (78.0), Rigel (78.1), Capella (78.4)
'5h (76.1)	'June 6 (157)	'7
Pleione 6	7	8


Ga1-15	*Ga1-16 (80)**	Ga1-17	Ga1-18	Ga1-19 (20)
	λ Leporis (79.6)	Bellatrix, Saif al Jabbar (80.7), Elnath (80.9)	Nihal (81.7), Mintaka (82.4)	ε Columbae (82.6), Arneb (83.0), Heka (83.2)
'June 8	'9	'10	'11	'12 (163)
Pleione 9	10	11	12	13

Pleione 13 is thus easy to associate with the very last day of the old year.

The manzil date Albatain 1 probably coincides with moe in Ga1-20:


Ga1-20 (21)	Ga1-21
Hatysa (83.5), Alnilam (83.7), Heavenly Gate (84.0)	Alnitak, Phakt (Phaet), (84.7)
'June 13	'14
Albatain 1 (28)	2


Ga1-22	Ga1-23	Ga1-24 (25)	Ga1-25	*Ga1-26 (90)**
γ Leporis (85.9)	Saiph (86.5), ζ Leporis (86.6)	Wezn (87.6), δ Leporis (87.7), Betelgeuze (88.3)	η Leporis (89.0), Praja-pāti, Menkalinan, Mahashim, and γ Columbae (89.3)	η Columbae (89.7), μ Orionis (90.3)
'June 15	'16	'17 (168)	'18	'19
Albatain 3	4	5	6	7

Summer solstice north of the equator mostly occurs in June 21, though sometimes in the day before:

Solstice

Ga1-27	Ga1-28	Ga1-29
χ² Orionis (90.5), ν Orionis (91.4)		ξ Orionis (92.5), Tejat Prior (93.4)
'6h (91.3)	'June 21 (172)	'22
Albatain 8	9 (36)	10


Ga1-30	*Ga2-1 (95)**
κ Aurigae (93.6)	Furud (94.9), Tejat Posterior, Mirzam (95.4)
'23 (St John's Eve)	'24 (St John's Day)
11	12

(Midsummer bonfire in Mäntsälä, Finland.)

South of the equator this time of the year is not in midsummer but in midwinter, it is not hot but cold:

...Because of the cold weather, nothing grows (tupu meme), and there is hardly any work done in the fields. Hens grow an abundance of feathers, which are used for the festivities. The time of the great festivities begins, also for the father-in-law (te ngongoro mo te hungavai). There is much singing (riu) ...