If we move 100 days backwards in time, from maro at Ca6-24, we arrive at Friday:

96
Ca3-14 (65) Ca3-15 Ca3-16 Ca6-24 (164)
100

In the text of H Venus has been identified as a probable location for the beginning of time:

189 747
Hb9-48 Hb9-49 Hb9-50 Hb3-4 Hb3-5 Hb3-6 (753)
 day 1 63 249 day 250 + 64 = 314

In G we have put Rogo in this position:

63 + 235
Gb6-25 Gb6-26 (1) Gb1-6 Gb1-7 (301)

Maro in Ca6-24 from that perspective seems to acquire a function of marking the end of the first 100 days. This idea finds support in the text of G, where manu rere in Ga4-16 is day number 100 (counted from Cb8-30):

13
Ga4-16 (100) Ga4-17 Ga4-18 Ga4-19

Obviously this glyph is the last of some season, because then follows a Rei glyph. (And 4 * 16 = 64.)