diff --git a/access/course.py b/access/course.py
index 1b0c7d6..fc5e3e3 100644
--- a/access/course.py
+++ b/access/course.py
@@ -21,6 +21,15 @@
 LOGGER = logging.getLogger('main')
 
 
+def _get_datetime(value: Any) -> Optional[datetime]:
+    """Turns date/datetime into a datetime and returns None if given anything else"""
+    if isinstance(value, date):
+        return datetime.combine(value, datetime.max.time())
+    elif not isinstance(value, datetime):
+        return None
+    return value
+
+
 class ConfigureOptions(PydanticModel):
     files: Dict[str,str] = {}
     # ellipsis (...) makes the field required in the case that a default url isn't specified
@@ -354,6 +363,27 @@ def name_or_title(cls, values: Dict[str, Any]):
             values["name"] = values.pop("title")
         return values
 
+    @root_validator(allow_reuse=True, skip_on_failure=True)
+    def validate_dates(cls, values: Dict[str, Any]) -> Dict[str, Any]:
+        close = values.get("close")
+        close_dt = _get_datetime(close)
+        
+        open = values.get("open")
+        open_dt = _get_datetime(open)
+        if open_dt and close_dt and open_dt > close_dt:
+            raise ValueError(f"Module 'close' ({close}) before 'open' ({open})")
+
+        late_close = values.get("late_close")
+        late_close_dt = _get_datetime(late_close)
+        if late_close_dt and close_dt and late_close_dt < close_dt:
+            raise ValueError(f"'late_close' ({late_close}) is before 'close' ({close})")
+
+        read_open = values.get("read_open")
+        read_open_dt = _get_datetime(read_open)
+        if read_open_dt and open_dt and read_open_dt >= open_dt:
+            raise ValueError(f"'read_open' ({read_open}) is not before 'open' ({open})")
+
+        return values
 
 NumberingType = Literal["none", "arabic", "roman", "hidden"]
 
@@ -469,24 +499,26 @@ def validate_keys(cls, values: Dict[str, Any]) -> Dict[str, Any]:
 
     @root_validator(allow_reuse=True, skip_on_failure=True)
     def validate_module_dates(cls, values: Dict[str, Any]) -> Dict[str, Any]:
-        def get_datetime(value):
-            if isinstance(value, date):
-                return datetime.combine(value, datetime.max.time())
-            elif not isinstance(value, datetime):
-                return None
-            return value
-
-        end_date = get_datetime(values.get("end"))
-        for m in values["modules"]:
-            close = get_datetime(m.close)
-            if close and end_date and close > end_date:
-                m.add_warning(f"Course ends before module closes")
-
-            late_close = get_datetime(m.late_close)
-            if late_close:
-                if close:
-                    if late_close < close:
-                        m.add_warning(f"'late_close' is before 'close'")
-                elif end_date and late_close < end_date:
-                    m.add_warning(f"'late_close' is before module close (which defaults to course 'end')")
+        end = values.get("end")
+        end_dt = _get_datetime(end)
+        for i, m in enumerate(values["modules"]):
+            close_dt = _get_datetime(m.close)
+            if close_dt and end_dt and close_dt > end_dt:
+                m.add_warning(f"Course 'end' ({end}) before module {i} 'close' ({m.close})", "close")
+
+            late_close_dt = _get_datetime(m.late_close)
+            if late_close_dt and not close_dt and end_dt and late_close_dt < end_dt:
+                raise ValueError(f"Module {i} 'late_close' ({m.late_close}) is before 'close' ({end}, defaulted to course 'end')")
+        return values
+
+    @root_validator(allow_reuse=True, skip_on_failure=True)
+    def validate_course_dates(cls, values: Dict[str, Any]) -> Dict[str, Any]:
+        start = values.get("start")
+        end = values.get("end")
+        start_dt = _get_datetime(start)
+        end_dt = _get_datetime(end)
+
+        if start_dt and end_dt and start_dt > end_dt:
+            raise ValueError(f"Course 'end' ({end}) before 'start' ({start})")
+
         return values