nobody

Information

Application settings.
Security > Database session > Initialization PL/SQL Code
execute immediate 'ALTER SESSION SET NLS_TERRITORY=''AMERICA''';
execute immediate 'ALTER SESSION SET NLS_SORT=''BINARY_CI''';
execute immediate 'ALTER SESSION SET NLS_NUMERIC_CHARACTERS='',.''';
execute immediate 'ALTER SESSION SET NLS_CURRENCY=''€''';

Globalisation >
Application Date Format => DD-MM-YYYY
Application Primary Language => Dutch(Netherlands)(nl)

Click on the one of the links to see the effect the difference in show and accept
with regard to implicit date conversion.

When the date is shown as display only and no format mask is applied then there 
is an implicit date conversion done at the moment of calculating the checksum in the database.
A difference in the wwv_flow.show versus wwv_flow.accept functions results in different database checksums being calculated.
Resulting in a impossibility of saving the record.

Debug reveals an extra "Setting NLS_DATE_FORMAT to application date format: DD-MM-YYYY" statement upon show after the 
execute immediate 'ALTER SESSION SET NLS_TERRITORY=''AMERICA''';
is executed.

Upon accept there is no "Setting NLS_DATE_FORMAT to application date format: DD-MM-YYYY" happening after 
Database session > Initialization PL/SQL Code is executed.

This checksum error doesn't occur when the date item is datepicker.
Probably because the default formatmask is the application date formatmask.
And a explicit date conversion is done.
The same happens when the formatmask is set for the display only item.