diff --git a/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/fhirpath/FHIRPathEngine.java b/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/fhirpath/FHIRPathEngine.java
index 2bb17918b..0795f7c7e 100644
--- a/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/fhirpath/FHIRPathEngine.java
+++ b/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/fhirpath/FHIRPathEngine.java
@@ -2748,15 +2748,12 @@ public class FHIRPathEngine {
       result.add(new IntegerType(Integer.parseInt(l.primitiveValue()) + Integer.parseInt(r.primitiveValue())));
     } else if (l.hasType("decimal", "integer") && r.hasType("decimal", "integer")) { 
       result.add(new DecimalType(new BigDecimal(l.primitiveValue()).add(new BigDecimal(r.primitiveValue()))));
-    } else if ((l.isDateTime() || l.hasType("date")) && r.hasType("Quantity")) {
-      if (l.hasType("date")) {
-        BaseDateTimeType dt = l instanceof BaseDateTimeType ? (BaseDateTimeType) l : TypeConvertor.castToDateTime(l);
-        Quantity qty = r instanceof Quantity ? (Quantity) r : TypeConvertor.castToQuantity(r);
-        result.add(dateAdd(dt, qty, false, expr));
-      } else {
-        DateTimeType dl = l instanceof DateTimeType ? (DateTimeType) l : new DateTimeType(l.primitiveValue());
-        result.add(dateAdd(dl, (Quantity) r, false, expr));
-      }
+    } else if (l.hasType("date") && r.hasType("Quantity")) {
+      DateType dl = l instanceof DateType ? (DateType) l : new DateType(l.primitiveValue()); 
+      result.add(dateAdd(dl, (Quantity) r, false, expr));
+    } else if ((l.isDateTime() || l.hasType("dateTime") || l.hasType("instant")) && r.hasType("Quantity")) {
+      DateTimeType dl = l instanceof DateTimeType ? (DateTimeType) l : new DateTimeType(l.primitiveValue()); 
+      result.add(dateAdd(dl, (Quantity) r, false, expr));
     } else {
       throw makeException(expr, I18nConstants.FHIRPATH_OP_INCOMPATIBLE, "+", left.get(0).fhirType(), right.get(0).fhirType());
     }
@@ -3001,7 +2998,7 @@ public class FHIRPathEngine {
     if (right.size() > 1) {
       throw makeExceptionPlural(right.size(), expr, I18nConstants.FHIRPATH_RIGHT_VALUE, "-");
     }
-    if (!right.get(0).isPrimitive() &&  !((left.get(0).isDateTime() || left.get(0).hasType("date", "dateTime") || "0".equals(left.get(0).primitiveValue()) || left.get(0).hasType("Quantity")) && right.get(0).hasType("Quantity"))) {
+    if (!right.get(0).isPrimitive() &&  !((left.get(0).isDateTime() || left.get(0).hasType("date", "dateTime", "instant") || "0".equals(left.get(0).primitiveValue()) || left.get(0).hasType("Quantity")) && right.get(0).hasType("Quantity"))) {
       throw makeException(expr, I18nConstants.FHIRPATH_RIGHT_VALUE_WRONG_TYPE, "-", right.get(0).fhirType());
     }
 
@@ -3019,15 +3016,12 @@ public class FHIRPathEngine {
         Quantity qty = (Quantity) r;
         result.add(qty.copy().setValue(qty.getValue().abs()));
       }
-    } else if ((l.isDateTime() || l.hasType("date", "dateTime", "instant")) && r.hasType("Quantity")) {
-      if (l.hasType("date")) {
-        BaseDateTimeType dt = l instanceof BaseDateTimeType ? (BaseDateTimeType) l : TypeConvertor.castToDateTime(l);
-        Quantity qty = r instanceof Quantity ? (Quantity) r : TypeConvertor.castToQuantity(r);
-        result.add(dateAdd(dt, qty, true, expr));
-      } else {
-        DateTimeType dl = l instanceof DateTimeType ? (DateTimeType) l : new DateTimeType(l.primitiveValue());
-        result.add(dateAdd(dl, (Quantity) r, true, expr));
-      }
+    } else if (l.hasType("date") && r.hasType("Quantity")) {
+      DateType dl = l instanceof DateType ? (DateType) l : new DateType(l.primitiveValue()); 
+      result.add(dateAdd(dl, (Quantity) r, true, expr));
+    } else if ((l.isDateTime() || l.hasType("dateTime") || l.hasType("instant")) && r.hasType("Quantity")) {
+      DateTimeType dl = l instanceof DateTimeType ? (DateTimeType) l : new DateTimeType(l.primitiveValue()); 
+      result.add(dateAdd(dl, (Quantity) r, true, expr));
     } else {
       throw makeException(expr, I18nConstants.FHIRPATH_OP_INCOMPATIBLE, "-", left.get(0).fhirType(), right.get(0).fhirType());
     }