47. According to Lampridius (Hist. August. p. 135),
Alexander Severus lived twenty-nine years, three months, and
seven days. As he was killed March 19, 235, he was born
December 12, 205, and was consequently about this time
thirteen years old, as his elder cousin might be about
seventeen. This computation suits much better the history of
the young princes, than that of Herodian (1. v. p. 181), who
represents them as three years younger; whilst, by an
opposite error of chronology, he lengthens the reign of
Elagabalus two years beyond its real duration. For the
particulars of the conspiracy, see Dion, 1. lxxviii. p.
1339. Herodian, 1. v. p. 184.