derivedDataType MtasDateDT

EcimDerivedString at 10 characters (yyyy-mm-dd), in the following regexp format:
([0-9]{4})[-](0[1-9]|1[012])[-](0[1-9]|[12][0-9]|3[01])

References from:
MtasMmtCalPubHoliday; VtasMmtCalPubHoliday;
stringMtasDateDT

Valid values: ([0-9]{4})[-](0[1-9]|1[012])[-](0[1-9]|[12][0-9]|3[01])|^$
  derivedDataType MtasDateDT