Category:Language articles with invalid population dates
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This category is triggered if something other than a purely numerical value is entered in the date field of a language infobox. (Note that this does not happen if a merely unlikely date is entered.) An invalid input affects the display of the infobox as well as its ability to detect obsolete data.
Entering 'NA' or 'no date' in the date field triggers a subcategory. Though it does not cause any problems with display, it does prevent the obsolescence calculation.