In Heraclium is the earliest extant poem by George of Pisidia. The poem does not contain reference to the date of its composition, nor is any external evidence present. Overall, the main assumption has been that it was written to celebrate Heraclius’ ascent to the throne, after his victory in a revolt against the usurper Phocas. The two main datings are late 610 - early 611 CE, or 618 CE. The present study shows discrepancies between the rules for the panegyrical genre, which the poem is usually ascribed to, and its actual content. The main differences are absence of any reference to Heraclius’ background and lack of proper treatment of Heraclius as an emperor. The article shows that all these features are present in the majority of survived verse and prose panegyrics to the emperors, whether they are in Greek or in Latin. Moreover, the poem digresses from the rules set out for an imperial panegyric by the Greek rhetorician Menander, whose recommendation George of Pisidia normally follows, as it has been show