About the American Ordo The American Ordo is a guide to the Mass and the Liturgy of the Hours for each day. Celebrations proper to the United States are noted. For celebrations below the rank of feast the citations for the readings are from the Season of the year. Proper readings are noted for some dates. For pastoral reasons one may choose readings that are appropriate to the occasion. On solemnities, feasts and memorials which have a proper preface, Eucharistic prayer IV should not be used because the prefaces for the days are an integral part of the Mass text for that day. Your comments on this Ordo are welcome.