Upgrading from V3

First, please make sure you read the full documentation.

There are a few changes in v4 that require changes to your templates.

General

Output of the tags are now full entries, so all normal entry variables are available.
There is no {{ dates }} pair anymore, now data is returned just like the collection tag. So if you had:

{{ events:upcoming .... }}
  {{ dates }}
    ....
  {{ /dates }}
{{ /events:upcoming }}

It would now look like:

{{ events:upcoming .... }}
    ....
{{ /events:upcoming }}

There is no special {{ date }} variable any more. Instead there is {{ start }} and {{ end }}.

Instead of {{ ... paginate="true" limit="5" }} you now do {{ ... paginate="5" }}, just like the collection tag.
Output is now like the collection tag's output and has a {{ results }} variable pair and a {{ paginate}} pair