Translations:Surveys - introduction/130/en
From LimeSurvey Manual
Attention : If this feature is activated, the response submission date and the token completed date are always set to 1980-01-01 00:00, regardless of other settings. Invalidating the submission date ensures no match with the web server logs where the token key might show up when a survey is started. Invalidating the token completed date guarantees that you cannot align the order of submitted responses to the order of the token date/time.