It is necessary to decide on a default date format and then stick with it. Natural relies on a consistent date format across sessions, libraries, programs, etc. That is, you want all your date literals in the same format, across all your applications.
Date format is determined by the DTFORM parameter. http://techcommunity.softwareag.com/ecosystem/documentation/naturalONE/natONE911/core/using/use-prefer.htm#use-prefer-regional-opt
- I International yyyy-mm-dd default
Looks like you had the default setting when it worked before, but now have DTFORM=E. To use the yyyy-mm-dd format for your date literal (D’2500-12-31’), change the setting to DTFORM=I.
Using NaturalONE --> Setting the Preferences --> Regional Setttings --> Options --> DTFORM
(NOTE: Natural is smart enough to let you have users in different locales input different date formats while executing the same application.)