@markewallace This is the way I am doing it now, because it's important not to have startDate: null|undefined as part of the args object. There was also a problem where I was going to try to validate if a date is ISO formatted, but the Date class doesn't let me do this and a regular expression would get very complex. Just going to check they are there and if there are any problems the server will respond with invalid date format, is that ok?