Sub convertir()
Dim tablo() As Variant
With ActiveSheet
fin = .Range("A" & .Rows.Count).End(xlUp).Row
tablo = .Range("A2:A" & fin).Value
End With
For i = LBound(tablo, 1) To UBound(tablo, 1)
tablo(i, 1) = Format(tablo(i, 1) / 1440, "hh:mm:ss")
Next i
Range("M2:M" & fin) = tablo
End Sub