Change date from 2015/02/23 to “1 min ago”

Here you go. This goes in functions.php

This changes the time on your website everywhere. Now you can keep using <?php echo get_the_date(); ?> in your loop or theme files.

// Relative date & time
function wpse_relative_date() {
  return human_time_diff( get_the_time('U'), current_time( 'timestamp' ) ) . ' ago';
}
add_filter( 'get_the_date', 'wpse_relative_date' ); // for posts and pages
// add_filter( 'get_comment_date', 'wpse_relative_date' ); // for comments

I added a PHP comment before add_filter to also change comment dates too. Because I am not sure if you want that for comments too. Remove PHP comment if needed.