How can I use Cron on Google App Engine?
Google has officially enabled cron in the AppEngine, for more details check:
Cron for Python: http://code.google.com/appengine/docs/python/config/cron.html
Cron for Java: http://code.google.com/appengine/docs/java/config/cron.html
Here's a tutorial on using a Google App Engine Cron Job to send an automated email:
http://www.fishbonecloud.com/2010/11/automated-email-using-google-app-engine.html
Read comments to issue 6 for possible workarounds.
You can use GAE Cron jobs, but be careful as they don't support HTTPS!