Force scheduled tasks to run now?

Hi,
Just wondering, is there a way to force a scheduled task to run “now”?
In particular, I’ve just enabled old log purging but I don’t want to wait about 20 hours before I see how it goes.

I’ve had a look at the piwik_options table and tried changing the stuff in ‘TaskScheduler.timetable’, but the admin interface still says it’ll run in ~20 hours time.

I’ve tried running archive.sh regardless, and it says that it ran the delete logs task

Starting Scheduled tasks...

task,output
Piwik_PrivacyManager.deleteLogTables,Time elapsed: 0.001s
Finished Scheduled tasks.

But old log entries still appear to be in the database.

Thanks!