Support validations of dates as milliseconds or seconds

internal/fields/validate.go

@@ -374,7 +374,7 @@ func (v *Validator) parseElementValue(key string, definition FieldDefinition, va
 		if err := ensurePatternMatches(key, valStr, definition.Pattern); err != nil {
 			return err
 		}
-	case "date", "keyword", "text":
+	case "keyword", "text":
 		var valStr string
 		valStr, valid = val.(string)
 		if !valid {
@@ -384,6 +384,22 @@ func (v *Validator) parseElementValue(key string, definition FieldDefinition, va
 		if err := ensurePatternMatches(key, valStr, definition.Pattern); err != nil {
 			return err
 		}
+	case "date":
+		switch val := val.(type) {
+		case string:
+			if err := ensurePatternMatches(key, val, definition.Pattern); err != nil {
+				return err
+			}
+			valid = true
+		case float64:
+			// date as seconds or milliseconds since epoch
+			if definition.Pattern != "" {
+				return fmt.Errorf("numeric date in field %q, but pattern defined", key)
+			}
+			valid = true
+		default:
+			valid = false
+		}
 	case "ip":
 		var valStr string
 		valStr, valid = val.(string)

internal/fields/validate_test.go

@@ -151,6 +151,22 @@ func Test_parseElementValue(t *testing.T) {
 				Pattern: "^[0-9]{4}(-[0-9]{2}){2}[T ][0-9]{2}(:[0-9]{2}){2}Z$",
 			},
 		},
+		{
+			key:   "date as milliseconds",
+			value: float64(1420070400001),
+			definition: FieldDefinition{
+				Type: "date",
+			},
+		},
+		{
+			key:   "date as milisecond with pattern",
+			value: float64(1420070400001),
+			definition: FieldDefinition{
+				Type:    "date",
+				Pattern: "^[0-9]{4}(-[0-9]{2}){2}[T ][0-9]{2}(:[0-9]{2}){2}Z$",
+			},
+			fail: true,
+		},
 		{
 			key:   "bad date",
 			value: "10 Oct 2020 3:42PM",