Решил вопрос не показывая числа по оси X
Изменив в библиотеке
xaxis: {
show: false, // null = auto-detect, true = always, false = never
и соответственно в графике указал порядковые номера дат
{ data: [
[10,<?php echo $publications_0_day_before;?>],
[9,<?php echo $publications_1_day_before;?>],
[8,<?php echo $publications_2_day_before;?>],
[7,<?php echo $publications_3_day_before;?>],
[6,<?php echo $publications_4_day_before;?>],
[5,<?php echo $publications_5_day_before;?>],
[4,<?php echo $publications_6_day_before;?>],
[3,<?php echo $publications_7_day_before;?>],
[2,<?php echo $publications_8_day_before;?>],
[1,<?php echo $publications_9_day_before;?>]