Automatically update lists gantt chart view to current month

Hi, I want this "yearly" gantt chart to display the current month forward and display the upcoming 18 months as well. I got the code from the yearly gantt chart view with today but im confused because it displays months and not years. and every edit ive made displays the code and not the value. 

https://github.com/pnp/List-Formatting/blob/master/column-samples/generic-yearly-gantt-chart/generic-yearly-gantt-chart.json