[FIX] point_of_sale: date string ECMA 5.1 in Date()

Before this commit, when opening the POS in IE11, then the customer list, the list was empty.
This was due to condition that was wrongly evaluated as false due to the fact that IE11 apparently only wants ECMA5.1 to deal with constructing Date() from a string.

After this commit, we construct the Date() object with the right string, and the list of customers doesn't disappear.

OPW 776463

For reference:
http://www.ecma-international.org/ecma-262/5.1/#sec-15.9.1.15

closes #20468