The development and widespread adoption of a uniform alphabet across all modern Mayan languages has solved a number of problems. Written forms of communication have been enhanced through standardization. Accuracy in pronouncing Mayan words from a written text, even when using a Mayan language with which one has limited familiarity, is now much higher. Because of its utility it might also be assumed that the modern Maya writing system would be applied to transcriptions of ancient Maya glyphs found in parchment documents, in paintings on walls and ancient pottery, as well as stone carvings that survive to this day. In fact, initially there was a tendency to abandon the old colonial-era orthography in favor of the new system.

Beginning in the late 1980s and especially in the 1990s, epigraphers backed away from these old conventions. Refinements in comparative linguistics and the direct participation of indigenous Mayan linguists led to more precise orthographies and standards across Mayan languages. Naturally epigraphers came to adopt these practices, and names for the days and months soon came to be represented just like any other term in Classic Mayan.

Source: David Stuart, A Note on Spelling Days and Months, Maya Decipherment May 1, 2016. https://decipherment.wordpress.com/2016/05/01/a-note-on-spelling-days-and-months/

However, not all epigraphers have followed suit. And in some cases, a single epigrapher may alternate systems based on a given circumstance. This inconsistency has actually increased in recent years leading to some confusion among students of Maya glyphs. There is, however, a method to this madness. Consider the following rationale advanced by David Stuart in a recent post on Maya Decipherment:

After many years of adopting what might seem a more accurate and linguistically sensitive orthography, I’ve now gone back to the old ways for writing dates, preferring for example to write “10 Chicchan 18 Uo” instead of “10 Chikchan 18 Woh.” The reason is quite simple. In most instances we have no direct evidence of how day names were pronounced in the Classic period. Was the first day Imix or Imox? Was the thirteenth day Ben, Been or something else? Ancient scribes wrote day names as logographs (word signs) and only rarely presented any phonetic indicators about pronunciation, thus leaving modern students with many questions, and employing the old Yukatek nomenclature should immediately make clear that these are not necessarily the ancient names for these time periods. I would never want a student to automatically assume that the fifth day was pronounced as Chikchan in eighth century Palenque; in fact it probably wasn’t.

Source: David Stuart, A Note on Spelling Days and Months, Maya Decipherment May 1, 2016. https://decipherment.wordpress.com/2016/05/01/a-note-on-spelling-days-and-months/

He goes on to note that in some cases we have clear evidence of how to transcribe glyphs, such as with the names of months on the Maya calendar because the corresponding glyphs are often true spellings. Such is the case with Ajaw, for example, which is considered a solid reconstruction (thus favoring an abandonment of the former writing convention of Ahau). In practice, however, it is still seen both ways.

"8 Ajaw" and "8 Woh" Maya glyphs

Date record “8 Ahau 8 Uo” (traditional form) “8 Ajaw 8 Woh” (modern standard form) from La Corona, Element 56. Photo by D. Stuart. Source: https://decipherment.wordpress.com/2016/05/01/a-note-on-spelling-days-and-months/

The points Stuart makes are good ones. Adopting the modern standard alphabet when transcribing ancient Maya glyphs might cause us to collapse or gloss over important regional and temporal variations in the ways those words were actually used and pronounced. Or it might imply that we know more than we actually do about how those ancient terms were vocalized. So a carefully considered approach to transcription, even if it is inconsistent, seems a sound and cautious approach. Far more tantalizing, however, is the prospect that further research into the ancient Maya culture and its writing system could indeed yield further breakthroughs in our understanding of their achievements in language. And Stuart, who of course knows this better than anyone, obliquely hints at this in the conclusion to his post that I have quoted extensively here:

It is still important to realize that we are still in a relatively early stage in the true decipherment of the Maya hieroglyphic system, most of which took place only in the last three or so decades. It shouldn’t be surprising that Mayanists reassess and refine the standards we use for presenting epigraphic source material. It’s a continuous process.

Source: David Stuart, A Note on Spelling Days and Months, Maya Decipherment May 1, 2016. https://decipherment.wordpress.com/2016/05/01/a-note-on-spelling-days-and-months/