Ancient Egyptian, as one of the longest attested languages, constitutes a notable example for the study of linguistic change in a diachronic perspective. Among the chronolects of Ancient Egyptian, Égyptien de Tradition (ÉdT) exhibits the longest life span with approximately 1500 yrs., ranging from ~ 1100 BCE to ~ 400 CE. ÉdT coexisted with Late Egyptian, Demotic and even early Coptic rendering it a particularly interesting case of diglossia. Texts belonging to this variety emulate classical Middle Egyptian, while being strongly influenced by contemporaneous chronolects, such as Late Egyptian and Demotic. In scholarly debate, the presence or lack of Middle Egyptian features was used as a vantage point to identify and separate old texts from new ones. The linguistic evaluation of these textual varieties, in turn, has, severe consequences for how we conceptualize the philological capacities and practices of Ancient Egyptians of the Late and Ptolemaic Periods. Given the diachronically heterogeneous nature of of Égyptien de tradition’s grammatical properties, this Chronoi project aims at developping a linguistic annotation that will, in turn, enable us to detect clusters and trends of Égyptien de tradition, enhancing our understanding of linguistic registers and scribal text production in the Ptolemaic Period. At its core, the project analyzes the Ptolemaic Synodal Decrees in comparison with central texts of this chronolect. The project „Diglossia in Ptolemaic Egypt“ collaborates with the Akademienvorhaben “Strukturen und Transformationen des Wortschatzes der Ägyptischen Sprache. Text- und Wissenskultur im Alten Ägypten“ at the Berlin-Brandenburg Academy of Sciences and the Humanities.