improved datetime parsing robustness for miliscond

ketos/data_handling/data_handling.py

@@ -91,7 +91,8 @@ def parse_datetime(to_parse, fmt=None, replace_spaces='0'):
                 See https://pypi.org/project/datetime-glob/ for a list of valid directives. 
                 In addition to the directives allowed by the datetime-glob package, it is 
                 also possible to specify %S.%ms for milliseconds. Note that the milliseconds
-                (%ms) must follow the seconds (%S) separated by a period (.).               
+                (%ms) must follow the seconds (%S) separated by a period (.) and can only be 
+                followed by an asterisk (*) or nothing.            
             replace_spaces: str
                 If string contains spaces, replaces them with this string