Date datatype behaving differently in Chrome and IE

Hello, 
So I have some JSON date like this : 
{
"WEEK" : "01-01-2018",
"X" : <SOME VALUE>,
"Y" : <SOME VALUE>
}
 
My slice : 
"rows": [
{
"uniqueName":"[Measures]"
}
],
"columns": [
{
"uniqueName":"WEEK"
}
],
"measures: : [
{
 <<<measured values>>>>
}]
 
 
Note that the "WEEK" field is of String type and not DATE type.
Everything works as expected on Chrome and firefox.
 
But the date column is being displayed hierarchically (WEEK.DAY, WEEK.MONTH, WEEK.YEAR) on Internet Explorer. I don't understand this different behavior on IE. I want to display the column like a string - like it does on Chrome.
Could you guys help me solve this issue? Thank you.