In the Keiti calendar for the year GD16 appears in the 6th and the 15th periods:

6			2 glyphs. Moon (the winter season), at left in Eb3-8, is 'finished', i.e. 'has left'.
	Eb3-7	Eb3-8
	Eb3-9	Eb3-10	Eb3-11	Eb3-12	Eb3-13	Eb3-14	Eb3-15	Eb3-16
				2 + 8 + 3 = 13 glyphs
	Eb3-17	Eb3-18	Eb3-19
15			GD15 (tagata) suggests the season of GD16 is fully grown, and the 6-feather maro marks its end.
	Eb4-26	Eb4-27

From 6 up to and including 15 there are 10 periods, a significant figure.