Date range for pg_stat_all_tables?

Hi -

I have the following query on pg_stat_all_tables to look at updates,
inserts, and deletes:

SELECT relname, n_tup_ins, n_tup_upd, n_tup_del FROM pg_stat_all_tables;

How can I add a date range to the WHERE clause to show data from a
specified date range?

I don't see anything in the table or in possible joins that will provide
dates.

Thanks for any assistance that can be provided.

Ronit