I have a model where one field is a date. I want to display elements from that model, grouped by year and by month, like this:

```
== 2013 ==
=== April ===
* Element 1
* Element 2
=== March ===
* Element 3
...
== 2012 ==
...

```

What if the best way to achieve that? Should I build a nested array directly in the Controler? Or is there a way to display the year and month headers only using Fluid template? Or should I write a custom ViewHelper to extract and display the year and month headers?