This is the point on which everything else depends, and it is not a matter of opinion. The Maya Tzolk'in, a 260-day count of thirteen numbers against twenty named days, is genuinely ancient, attested in Mesoamerica for well over two thousand years, and it is still kept, unbroken, by ajq'ijab' or daykeepers in the Guatemalan highlands, among the K'iche', Kaqchikel, Mam and other Maya peoples.
The Dreamspell count is not that count. It is anchored to the Gregorian calendar by a fixed correlation of Arguelles's own choosing, and, crucially, it skips 29 February, so that its kin and the traditional kin drift apart by one day every leap year and cannot be reconciled. The Day Out of Time has no Maya precedent. The thirteen-moon 28-day year is not a Maya calendar at all; the Maya solar count is the 365-day Haab of eighteen months of twenty days plus five. The seal names are also not translations of the Maya day names: several, notably Wizard, Warrior and Skywalker, replace the attested meanings with new ones.