Identifying time of last stat reset via sql

I asked this on general, but didn't receive any responses. Is it possible
via SQL to identify the time of the last stat reset (or pg_stat_reset()
call)? This is what I'm lacking to be able to measure query activity
volume over time via SQL, i.e., maybe a function similar to the fictitious
pg_stat_get_last_reset_time() below:

select sum(n_tup_ins + n_tup_upd + n_tup_del)
/ (now() - pg_stat_get_last_reset_time()) as write_qps
from pg_stat_all_tables

If not, would this be considered worthy of a TODO item? Or is there another
approached designed for determining QPS, etc?

Ed