Hi Peter,
In order to style the DateTimePicker, please refer to: https://www.htmlelements.com/docs/datetimepicker-css/. The documentation tutorial will help you to learn which CSS variables can be used for styling the Web Component.
Please, let us know if you have additional questions.
Best Regards,
B. Markov
SmartHtmlElements Team
https://www.htmlelements.com