Querying all Opportunities since a specific timestamp from the REST API

I have been tasked with building an integration with the Sugar CRM API Version 11_9 that needs to be able to read all Opporutnites that have been created or modified after specific timestamp.  Consider the following simplified data set. 

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[
{
id:"1",
"date_modified":"2020-08-10T03:09:09-08:00"
},
{
id:"2",
"date_modified":"2020-08-12T03:09:09-08:00"
},
{
id:"3",
"date_modified":"2020-08-14T03:09:09-08:00"
},
{
id:"4",
"date_modified":"2020-08-16T03:09:09-08:00"
},
]
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
I am needing to be able to call something like {{base_url}}/rest/v11_9/Opportunities?since=2020-08-13T03:09:09-08:00 and return 
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[
{
id:"3",
"date_modified":"2020-08-14T03:09:09-08:00"
},
{
id:"4",
"date_modified":"2020-08-16T03:09:09-08:00"
},
]
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
Any ideas on how to this?  This route isn't documented inside the REST API documentation so most everything I have had to figure out through inspection of API calls made vis the CRM Client application.  
Any help on figure out how this should be done is greatly appreciated.  Thanks!