Hello Andris,

UltraDateTimeEditor uses MS MonthCalendar control as its drop down. As MonthCalendar control does not allows changing of months’ names there is no way to change them in UltraDateTimeEditor. As a workaround you may consider to change UltraDateTimeEditor with UltraCalendarCombo. You can assign to the UltraCalendarCombo UltraCalendarInfo component and set the names of the months in the component like this:

this.ultraCalendarCombo1.CalendarInfo = this.ultraCalendarInfo1;
this.ultraCalendarInfo1.MonthsOfYear[YearMonthEnum.January].ShortDescription = "1";
this.ultraCalendarInfo1.MonthsOfYear[YearMonthEnum.January].LongDescription = "First month of the year";

Attached is a small sample where I have implemented this approach.

Please let me know if you have any additional questions.