Chris, historical data is stored in alert_recs table, alert details (i.e. name, owner, etc.) are in workspace_file table.
The command may look like this:
select date_trunc('day', a.time_stamp), count(a.guid)
from alert_recs a
JOIN workspace_file as w ON a.alert_guid = cast(w.id as varchar)
where
w.name = 'VM Disk Latency' -- name of the alert
and a.time_stamp > now() - interval '100 days' -- set least date
and a.raised = true
and a.statechange = true
group by date_trunc
Run the SQL query directly over the database and you will get the results. To allow users to connect the VMAN database please see this thread.
By default the alert_recs table contains one year historical data. You can change it in VMAN: modify months.to.keep.alerts property in Setup - System Properties menu .
Please let us know if it fits your needs.