Prior to version 8.1.0 the date-entry control used to send a NTF-CHANGED event once a date was selected, in version 8.1.0 the control sends an event for every click. This causes the calendar to close immediately, rendering the calendar control largely useless. If you do not specify the NOTIFY-CHANGE property on the DATE-ENTRY, there is no way of knowing the user changed the date.
This problem was fixed in version 8.1.1 with ecn-3886, there is no available patch for version 8.1.0, the only solution is to upgrade the runtime to 8.1.1 or later. The programs can be compiled with any previous version and be executed with the 8.1.1 runtime.