The localized Helper textValue(specified by Field Value) is not displaying for Datetime fields. it's expecting field value for pyCaption ,however ,it didn't work with pyActionPrompt,pyLabel,pyCaption & pyToolTip as well .
The problem you reported is identified as a Product Bug in Pega 8.x. The link provided to refer the product bug in Pega 7.2 is a tool tip, it is different from Helper Text design and configuration in Pega 8.x
The problem exist for DateTime and Checkbox controls. The fix is identified by the teams and the fix is going to be available from 8.3.2 patch release. For more information on patch release, Please visit