Why the date is displayed as “undefined” or this is not show?

Probably because you don’t choose the right date format. 'Time format' should be changed from the setting and usually the correct types are:

1: Change the Date Header Format Format in Format Panel

Go to:

Dashboard ›› Settings ›› Language and formatting ›› Date Header Format

2: Or Change the Timestamp Format in Format Panel

Go to:
 

Dashboard ›› Settings ›› Language and formatting ›› Timestamp Format

Now You've Done :)