 They occur in the weeks between the third and fourth Sundays of Advent, between the first and second Sundays of Lent, between Pentecost and Trinity Sunday, and beginning the first Wednesday after the Exaltation of the Holy Cross (September 14), which is between the liturgical third and fourth Sundays of September.Rogation Days are, in the calendar of the Western Church, four days traditionally set apart for solemn processions to invoke God's mercy.They are April 25, the Major Rogation (or Greater Litanies), coinciding with St. Mark's Day (but transferred to the following Tuesday if they fell on Easter); and the three days preceding Ascension Thursday, the Minor Rogations (or Lesser Litanies).