diff --git a/server/src/main/java/com/mirth/connect/client/core/api/providers/CalendarParamConverterProvider.java b/server/src/main/java/com/mirth/connect/client/core/api/providers/CalendarParamConverterProvider.java
index f194439702..486c89038f 100644
--- a/server/src/main/java/com/mirth/connect/client/core/api/providers/CalendarParamConverterProvider.java
+++ b/server/src/main/java/com/mirth/connect/client/core/api/providers/CalendarParamConverterProvider.java
@@ -10,7 +10,7 @@
 package com.mirth.connect.client.core.api.providers;
 
 import javax.inject.Singleton;
-import javax.ws.rs.ProcessingException;
+import javax.ws.rs.BadRequestException;
 import javax.ws.rs.ext.ParamConverter;
 import javax.ws.rs.ext.ParamConverterProvider;
 import javax.ws.rs.ext.Provider;
@@ -49,7 +49,7 @@ public T fromString(String value) {
                         T result = (T) calendar;
                         return result;
                     } catch (DateTimeParseException e) {
-                        throw new ProcessingException(e);
+                        throw new BadRequestException("Invalid date '" + value + "'. Expected format yyyy-MM-dd'T'HH:mm:ss.SSSZ, for example 1985-10-26T09:00:00.000-0700.", e);
                     }
                 }
 
diff --git a/server/src/test/java/com/mirth/connect/client/core/api/providers/CalendarParamConverterProviderTest.java b/server/src/test/java/com/mirth/connect/client/core/api/providers/CalendarParamConverterProviderTest.java
new file mode 100644
index 0000000000..e02f120d27
--- /dev/null
+++ b/server/src/test/java/com/mirth/connect/client/core/api/providers/CalendarParamConverterProviderTest.java
@@ -0,0 +1,51 @@
+// SPDX-License-Identifier: MPL-2.0
+// SPDX-FileCopyrightText: Open Integration Engine Contributors
+
+package com.mirth.connect.client.core.api.providers;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.fail;
+
+import java.util.Calendar;
+
+import javax.ws.rs.BadRequestException;
+import javax.ws.rs.core.Response;
+import javax.ws.rs.ext.ParamConverter;
+
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+public class CalendarParamConverterProviderTest {
+
+    private static ParamConverter<Calendar> converter;
+
+    @BeforeClass
+    public static void setup() {
+        converter = new CalendarParamConverterProvider().getConverter(Calendar.class, null, null);
+    }
+
+    @Test
+    public void testNullReturnsNull() {
+        assertNull(converter.fromString(null));
+    }
+
+    @Test
+    public void testValidDateRoundTrips() {
+        String value = "1985-10-26T09:00:00.000-0700";
+        Calendar calendar = converter.fromString(value);
+        assertNotNull(calendar);
+        assertEquals(value, converter.toString(calendar));
+    }
+
+    @Test
+    public void testInvalidDateThrowsBadRequest() {
+        try {
+            converter.fromString("1985");
+            fail("Expected BadRequestException for a malformed date");
+        } catch (BadRequestException e) {
+            assertEquals(Response.Status.BAD_REQUEST.getStatusCode(), e.getResponse().getStatus());
+        }
+    }
+}