[lightman]

This feast was created with the reform of the General Calendar in 1969. Many Roman martyrs feasts were removed from the General Calendar, since there wasn't too much historical information about them.

There is good logic in placing this feast immediately after the Festival of Sts. Peter and Paul, making this a sort of extension of that day, much as All Souls'Day is an extension and expansion of All Saints' Day.

[Salvation]

The thread I linked above has all the details of how these two commerations are joined.