How to execute batch based on records refresh?

Question

Requirement: Here I have Contacts, each of them is may/may not self-related to another Contact. Terminology: Primary Contact and Secondary Contact. Here Primary Contact is a self lookup field on the Contact object.

I am trying to push(using Upsert) some Opportunity records using data loader. For the newly created/updated Opportunity, if there is an OpportunityContactRole with a Secondary Contact(one which has a lookup to another Contact), check if there an OpportunityContactRole for the Primary Contact in regards to that Opportunity. If there is none, Create a new OpportunityContactRole for the Primary Contact.

Question: Things I am trying to achieve:

Opportunity records that are

1. Within a specific day range: Last 14 days/Last month
2. Last Modified/Created by a specific User(through out all dev orgs including Prod).

This is the query I had so far:

 Map<Id, Contact> relContIdsMap = new Map<Id, Contact>(secondaryCons);
 List<Opportunity> relatedOpps = [Select (Select OpportunityId From OpportunityContactRoles), Name 
                                From Opportunity Where Id IN 
                                (Select OpportunityId From OpportunityContactRole 
                                Where ContactId =: relContIdsMap.keySet())
                                AND (Opportunity.LastModifiedBy.LastName =: 'Data Load User' OR Opportunity.CreatedBy.LastName =: 'Data Load User'  )];
  System.debug('newOpps: ' +relatedOpps); //Returns the Opportunities of the Secondary contacts. 

How can I get the day range requirement full-filled? Any suggestions are welcome.

Background: I am trying to implement a Batch class which inserts new Contact Roles on the Opportunity based on:

1. User who updates the Opportunity, i.e., Data Load User
2. Last Modified date of the Opportunity record
3. If there is no Contact Role existed on the Primary Contact.

Answer 1

To fulfill the date range of Last 15 days or last month, use Date Literals LAST_N_DAYS:n or LAST_MONTH

Map<Id, Contact> relContIdsMap = new Map<Id, Contact>(secondaryCons);
 List<Opportunity> relatedOpps = [Select (Select OpportunityId From OpportunityContactRoles), Name 
                                From Opportunity Where Id IN 
                                (Select OpportunityId From OpportunityContactRole 
                                Where ContactId =: relContIdsMap.keySet())
                                AND (Opportunity.LastModifiedBy.LastName =: 'Data Load User' 
                                OR Opportunity.CreatedBy.LastName =: 'Data Load User' )
                                AND CreatedDate >= LAST_N_DAYS:15];

Also note that, this approach is good if you are running the batch with either 15 days or monthly interval respectively, so that same records will not be pulled twice.