Thank you for writing.
You should use the RadListDateItem's Text property instead of the Value property. The Value property is valid only for data-bound RadListDateItems and in your code the Value is null. Please, refer to the attached project.
A bit off topic, I would like to remind you that your subscription package has expired, which means that you are no longer entitled for our support services. I would highly recommend upgrading your license to the latest version in order to continue getting product updates and uninterrupted support services. Please, contact firstname.lastname@example.org
or visit your account for your upgrading options.
I hope this helps.
the Telerik team