The period of probation and instruction varied at different times and places:  according to Canon 42 of the Synod of Elvira, 305, it was to be two years:  “He who has a good name, and wishes to become a Christian, must be a Catechumen two years:  then he maybe baptized Hefele, Councils, i. p. 155.  Const. Apost. viii. 32:  “Let him that is to be instructed be a catechumen three years.”.”  After this probation had been satisfactorily passed, the Catechumens invited to give in their names as Candidates for Baptism.  This invitation, described by Cyril as a call to military service (κλῆσις στρατείας) Procat. § 1., appears to have been often repeated on the approach of Lent.  Thus S. Ambrose, in his Commentary on S. Luke, v. 5; We have toiled all night and have taken nothing, complains, “I too, Lord, know that for me it is night, when I have not Thy command.  No one yet has given his name:  with my voice I have cast the net throughout Epiphany, and as yet I have taken nothing.”