Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE customers_policies ( customer_id number, policy_id number, date_opened time, date_closed time )
TABLE: CREATE TABLE customers ( customer_id number, customer_name text )
TABLE: CREATE TABLE services ( service_id number, service_name text )
TABLE: CREATE TABLE available_policies ( policy_id number, policy_type_code text, customer_phone text )
TABLE: CREATE TABLE claims ( claim_id number, fnol_id number, effective_date time )
TABLE: CREATE TABLE settlements ( settlement_id number, claim_id number, effective_date time, settlement_amount number )
TABLE: CREATE TABLE first_notification_of_loss ( fnol_id number, customer_id number, policy_id number, service_id number )

### Question ###
What is the effective date of the claim that has the largest amount of total settlement?

### Accurate SQL ###

SELECT t1.effective_date FROM claims AS t1 JOIN settlements AS t2 ON t1.claim_id = t2.claim_id GROUP BY t1.claim_id ORDER BY SUM(t2.settlement_amount) DESC LIMIT 1