Calendar popup field get a default value. How to avoid this? I have all necessary module to add "Calendar popup" fields to my nodes. 

When creating a new node this field is populated with the current date. Since this field is not mandatory I need it empty by default. 

I can´t figure out how to accomplish this.  Please help.

I upload a capture
Edit the date field in your Content Type.  There should be a MORE SETTINGS AND VALUES accordion that drops down to reveal more options including DEFAULT VALUES.  Set the default value to No Default Value.  You probably have it set to Now.