If it did , he would have been made aware that it would be a day less than it used to be once he reached this line .
At the time , the concept of a de jure International Date Line did not exist .
If International Date Line did , he would have been made aware that it would be a day less than International Date Line used to be once he reached this line .
At the time , the concept of a de jure International Date Line did not exist .