For XPath you also have these tokens to use: https://docs.mendix.com/refguide/xpath-keywords-and-system-variables
Look at the [%BeginOfCurrentDayUTC%] and [%EndOfCurrentDayUTC%]. Do note that you need to decide which day you are going to use. Does the timezone of the user have to be taken into account? If not make sure that localize is set to off in your domain model. Otherwise you need the non UTC versions of these tokens.
Regards,
Ronald
You should use [%BeginOfCurrentDay%], see the doc here https://docs.mendix.com/refguide/xpath-keywords-and-system-variables
(and see the response of Ronald here : https://forum.mendix.com/link/questions/4522)