Managing a sharded cluster, http://docs.mongodb.org/manual/tutorial/manage-sharded-cluster-balancer/, has an option to set the Balancing Window. The example show how to set it to local time of the mongods. However if there are mongoses which are distributed in different timezones, this will defeat the purpose. It would be better if the example shows specifically how to set the the window in GMT (universal) time format, as an incorrect value is not handled by the Balancer, therefore causing it to not run.