You should refer to CRM dashboard in crm module to know how to create your reporting data using a SQL request in a custom module.

Then you will be able to add a domain like this in your XML file:

domain="[('<date_field>','&lt;=', ((context_today()+datetime.timedelta(days=60)).strftime('%%Y-%%m-%%d')))]"

Or you can create a filter like this in your list view to try to create the one you will add to your dashboard.

<filter
  string="Contracts ending in next 60 days"
  domain="[('<date_field>','&lt;=', ((context_today()+datetime.timedelta(days=60)).strftime('%%Y-%%m-%%d')))]"/>