AX World End Date

In some cases you will need to use the highest date available in a datetime field in Dynamics AX 2012.
Microsoft has decided that this date is:

December 31, 2154

Specifically when handling Date Effective Data in AX 2012, you might encounter date fields with the value "Never" when viewing it in the table browser. The field actually contains the date Dec 31, 2154.

When writing, updating or querying date effective records in x++, you can use the date 31\12\2154.
But a more accurate and less cryptic apporach would be to use the maxDate system function:

myDateEffectiveRecord.ValidTo = maxDate();