Does UTC date string require the format specifier "Z" even if that string includes time offset?

For instance,

const d = new Date("2012-08-20T15:00:00-07:00");

d here is a UTC time with time offset = 07:00. Does it still require Z like this 2012-08-20T15:00:00-07:00Z? Is this correct?

If I take this string with Z and parse it using Date.parse() method in JavaScript, it throws an error. Not sure what is wrong!