how can we define start date value in airflow for weekly or bi-weekly or monthly

Question

We are working on airflow currently. If we have any daily dags which has to run as we follow current date minus 1

if the dag(daily dag   00 10 * * *) should have first run on 20 March 2022 then we provide start date as  

'start_date': datetime(2022, 3, 19)

if we have to run on weekly basis or monthly basis, can any pls suggest how to provide start date ?

If the dag should run first on 19th march 2022(every saturday) cron 
expression : 00 10 * * 6 

what can i provide the start date in this case ? please suggest

is that something like 'start_date':

  datetime(2022, 3, 12) or 

 'start_date': datetime(2022, 3, 11) ?????

is there any way i can get start date based on frequency with some python code ?