Accordingly it cannot be mere accident, when we find a Christian feast very early fixed for this day. Gregory the Great recognised that people must not be all at once deprived of the old customs; he ordered that in England, at the dedication of churches and on the feasts of the martyrs, the newly converted Christians might retain some of the heathen customs which had been usual on similar occasions.[653] Instances in which this principle was put into practice are, for example, the processional litanies and the customs observed at the New Year. It is clear that the appointment of a Christian feast on the _Charistia_ is another instance of the tendency to deprive the heathen festivals of their harmful character. That this held good of the feast in question, and that a determined attempt was made to give it a Christian character, is shown by the fact that in other countries a different feast was appointed for this day. Polemius Silvius, Bishop of Sion, in the upper valley of the Rhone, composed a calendar for the year 448, the most ancient Christian calendar in existence, which he dedicated to Bishop Eucherius of Lyons.[654] In this document the heathen festivals are omitted, everything especially heathen has been removed, and only historical and meteorological notices remain; it contains some saints’ days, although very few in number. On the 22nd February we find the entry, _Depositio SS. Petri et Pauli_, along with a note on the _Charistia_, which shows that the intention of the writer was to supplant the heathen feast of the _Cara Cognatio_. Again, it is noteworthy that an event was chosen for this purpose which was commemorated in Rome, _i.e._ the burial of the two chief apostles. The 29th June was not then kept as a festival of the apostles in the upper valley of the Rhone, which belonged at that time to Gaul, and probably was not kept either in the whole province to which Sion (_Sedunum_) belonged.[655]