' s ▁letters ▁and ▁ser m ons ▁reflect ▁the ▁many ▁aspects ▁of ▁his ▁career ▁and ▁person ality ▁and ▁are ▁in valu able ▁historical ▁sources . ▁His ▁rh yth mic ▁pro se ▁style , ▁called ▁curs us ▁le onic us , ▁influenced ▁ecc les iast ical ▁language ▁for ▁centuries . ▁ ▁In ▁ 1 7 5 4 ▁Pope ▁Bened ict ▁XIV ▁proc laimed ▁Leo ▁I ▁a ▁Doctor ▁of ▁the ▁Church . ▁Next ▁to ▁Leo ▁only ▁one ▁other ▁po pe , ▁Gregory , ▁is ▁also ▁recognized ▁as ▁Doctor ▁of ▁the ▁Church . ▁ ▁The ▁Catholic ▁Church ▁marks ▁ 1 0 ▁November ▁as ▁the ▁fe ast ▁day ▁of ▁Saint ▁Leo , ▁given ▁in ▁the ▁Mart y ro log ium ▁Hier onym ian um ▁and ▁the ▁ 8 th - century ▁Calendar ▁of ▁Saint ▁Will ibr ord ▁as ▁the ▁date ▁of ▁his ▁death ▁and ▁entry ▁to ▁heaven . ▁His ▁fe ast ▁was ▁once ▁celebrated ▁in ▁Rome ▁on ▁ 2 8 ▁June , ▁the ▁anni versary ▁of ▁the ▁placing ▁of ▁his ▁re lic s ▁in ▁Saint ▁Peter ' s ▁Bas il ica , ▁but ▁in ▁the ▁ 1 2 th ▁century , ▁the ▁Gall ican ▁R ite ▁fe ast ▁of ▁ 1 1 ▁April ▁was ▁admitted ▁to ▁the ▁General ▁Roman ▁Calendar , ▁which ▁maintained ▁that ▁date ▁until ▁ 1 9 6 9 . ▁Some ▁traditional ist ▁C athol ics ▁continue ▁to ▁observe ▁pre - 1 9 7 0 ▁versions ▁of ▁that ▁calendar . ▁ ▁The ▁Eastern ▁Catholic ▁Church es ▁as ▁well ▁as ▁the ▁Eastern ▁Orth odox ▁Church ▁celebr