This flag explains why no appropriate value is in the field, RX Date Mst Defn Srg [3170]. This data item was first available in Volume II Version 12.
Before Version 12 (through 2009 diagnosis), date fields included codes that provided information other than dates. As part of an initiative to standardize date fields, new fields were introduced to accommodate non-date information that had previously been transmitted in date fields.
Comment: This is part of the initiative of the transformation from the old NAACCR date standards to interoperable dates.