The inline calendar of the datepicker sometimes has an issue when the month is changed.
For this tag <RadzenDatePicker Inline="true" TValue="DateTime" @bind-value="myobj.thedate" /> the calendar is displayed correctly. But if you select 31 January and then switch the month in the dropdown at the top of the calendar to February, the month does not get switched. It appears the control tries to set the date to February 31, which causes an exception.
System.ArgumentOutOfRangeException: Year, Month, and Day parameters describe an un-representable DateTime.
at System.DateTime.DateToTicks(Int32 year, Int32 month, Int32 day)
at System.DateTime..ctor(Int32 year, Int32 month, Int32 day, Int32 hour, Int32 minute, Int32 second)
1.SetMonth(Int32 month) at Radzen.Blazor.RadzenDatePicker1.b__0_12(ChangeEventArgs args)
The corrective behavior would seem to be to set the selected date to the last date of the month if that month does not have as many days as required by the previous selection. In the scenario above, selecting 31 January and then changing the month to February should change the selected date to 29 February.