Scholars long disputed whether Horemheb reigned for 14 or 27 years.
Manetho's Epitome assigns a reign length of 4 years and 1 month to Horemheb.
Scholars previously assigned this reign-length to Ay; however, evidence from excavations in Horemheb's tomb (KV57) indicates that this figure should be raised by a decade to [1]4 years and 1 month and attributed to Horemheb.
These excavations, conducted under G.T. Martin in 2006 and 2007, uncovered a large hoard of 168 inscribed wine sherds and dockets, below densely compacted debris in a great shaft (called Well Room E) in KV 57.
Of the 46 wine sherds with year dates, 14 have nothing but the year date formula, 5 dockets have year 10+X, 3 dockets have year 11+X, 2 dockets preserve year 12+X and 1 docket has a year 13+X inscription.
22 dockets "mention year 13 and 8 have year 14 [of Horemheb]" but none mention a higher date for Horemheb.

The full texts of the docket readings are identical and read as:
Year 13.
Wine of the estate of Horemheb-meren-Amun, L.P.H., in the domain of Amun.
Western River.
Chief vintner Ty.

Meanwhile, the year 14 dockets, in contrast, are all individual and mention specific wines such as "very good quality wine" or, in one case "sweet wine" and the location of the vineyard is identified.
A general example is this text on a year 14 wine docket:
Year 14, Good quality wine of the estate of Horemheb-meren-Amun, L.P.H., in the domain of Amun, from the wineyard of Atfih, Chief vintner Haty.

Other year 14 dockets mention Memphis (?),
the Western River while their vintners are named as Nakhtamun, [Mer-]seger-men, Ramose, and others.

The "quality and consistency of the KV 57 dockets strongly suggest that Horemheb was buried in his year 14, or at least before the wine harvest of his year 15 at the very latest."
This evidence is consistent "with the Horemheb dockets from Deir el-Medina which mention years 2, 3, 4, 6, 13, and 14, but again no higher dates ..." while a docket ascribed to Horemheb from Sedment has year 12."
The lack of dated inscriptions for Horemheb after his year 14 also explains the unfinished state of Horemheb's royal KV 57 tomb – "a fact not taken into account by any of those [scholars] defending a long reign [of 26 or 27 years].
The tomb is comparable to that of Seti I in size and decoration technique, and Seti I's tomb is far more extensively decorated than that of Horemheb, and yet Seti managed to virtually complete his tomb within a decade, whereas Horemheb did not even succeed in fully decorating the three rooms he planned to have done, leaving even the burial hall unfinished.
Even if we assume that Horemheb did not begin the work on his royal tomb until his year 7 or 8, ... it remains a mystery how the work could not have been completed had he lived on for another 20 or more years."
Therefore, most scholars now accept a reign of 14 years and 1 month.

 
The argument for a 27 year reign derived from two texts.
The first is an anonymous hieratic graffito written on the shoulder of a now fragmented statue from his mortuary temple in Karnak which mentions the appearance of the king himself, or a royal cult statue representing the king, for a religious feast.
The ink graffito reads Year 27, first Month of Shemu day 9, the day on which Horemheb, who loves Amun and hates his enemies, entered [the temple for the event].
It was disputed whether this was a contemporary text or a reference to a festival commemorating Horemheb's accession written in the reign of a later king.
The second text is the Inscription of Mes, from the reign of Ramesses II, which records that a court case decision was rendered in favour of a rival branch of Mes' family in year 59 of Horemheb.
It was argued that the year 59 Horemheb date included the reigns of all the rulers between Amenhotep III and Horemheb.
Subtracting the nearly 17 year reign of Akhenaten, the 2 year reign of Neferneferuaten, the 9 year reign of Tutankhamun and the reign of Ay suggested a reign of 26–27 years for Horemheb.
However, the length of Ay's reign is not actually known and Wolfgang Helck argues that t
Scholars long disputed whether Horemheb reigned for 14 or 27 years. Manetho's Epitome assigns a reign length of 4 years and 1 month to Horemheb. Scholars previously assigned this reign-length to Ay; however, evidence from excavations in Horemheb's tomb (KV57) indicates that this figure should be raised by a decade to [1]4 years and 1 month and attributed to Horemheb. These excavations, conducted under G.T. Martin in 2006 and 2007, uncovered a large hoard of 168 inscribed wine sherds and dockets, below densely compacted debris in a great shaft (called Well Room E) in KV 57. Of the 46 wine sherds with year dates, 14 have nothing but the year date formula, 5 dockets have year 10+X, 3 dockets have year 11+X, 2 dockets preserve year 12+X and 1 docket has a year 13+X inscription. 22 dockets "mention year 13 and 8 have year 14 [of Horemheb]" but none mention a higher date for Horemheb.
The full texts of the docket readings are identical and read as:
Year 13. Wine of the estate of Horemheb-meren-Amun, L.P.H., in the domain of Amun. Western River. Chief vintner Ty.
Meanwhile, the year 14 dockets, in contrast, are all individual and mention specific wines such as "very good quality wine" or, in one case "sweet wine" and the location of the vineyard is identified. A general example is this text on a year 14 wine docket:
Year 14, Good quality wine of the estate of Horemheb-meren-Amun, L.P.H., in the domain of Amun, from the wineyard of Atfih, Chief vintner Haty.
Other year 14 dockets mention Memphis (?), the Western River while their vintners are named as Nakhtamun, [Mer-]seger-men, Ramose, and others.
The "quality and consistency of the KV 57 dockets strongly suggest that Horemheb was buried in his year 14, or at least before the wine harvest of his year 15 at the very latest." This evidence is consistent "with the Horemheb dockets from Deir el-Medina which mention years 2, 3, 4, 6, 13, and 14, but again no higher dates ..." while a docket ascribed to Horemheb from Sedment has year 12." The lack of dated inscriptions for Horemheb after his year 14 also explains the unfinished state of Horemheb's royal KV 57 tomb – "a fact not taken into account by any of those [scholars] defending a long reign [of 26 or 27 years]. The tomb is comparable to that of Seti I in size and decoration technique, and Seti I's tomb is far more extensively decorated than that of Horemheb, and yet Seti managed to virtually complete his tomb within a decade, whereas Horemheb did not even succeed in fully decorating the three rooms he planned to have done, leaving even the burial hall unfinished. Even if we assume that Horemheb did not begin the work on his royal tomb until his year 7 or 8, ... it remains a mystery how the work could not have been completed had he lived on for another 20 or more years." Therefore, most scholars now accept a reign of 14 years and 1 month.
 
The argument for a 27 year reign derived from two texts. The first is an anonymous hieratic graffito written on the shoulder of a now fragmented statue from his mortuary temple in Karnak which mentions the appearance of the king himself, or a royal cult statue representing the king, for a religious feast. The ink graffito reads Year 27, first Month of Shemu day 9, the day on which Horemheb, who loves Amun and hates his enemies, entered [the temple for the event]. It was disputed whether this was a contemporary text or a reference to a festival commemorating Horemheb's accession written in the reign of a later king. The second text is the Inscription of Mes, from the reign of Ramesses II, which records that a court case decision was rendered in favour of a rival branch of Mes' family in year 59 of Horemheb. It was argued that the year 59 Horemheb date included the reigns of all the rulers between Amenhotep III and Horemheb. Subtracting the nearly 17 year reign of Akhenaten, the 2 year reign of Neferneferuaten, the 9 year reign of Tutankhamun and the reign of Ay suggested a reign of 26–27 years for Horemheb. However, the length of Ay's reign is not actually known and Wolfgang Helck argues that t
Horemheb