JavaScript filter code

I'm using vue 2.0

I need to filter an array of objects that has the following value

project_end_date: "2025-03-31T12:03:00Z"

The project_end_date will be different for each object but I only want to have the objects that the date is greater than 6 months less than today. The code that I'm trying to use is

const today = new Date();
code to add today = today minus 6 months

this.fundingData = this.fundingData.filter(item => item.project_end_date >= today);

I'm missing something and I'm willing to hire to fix it.

Thanks