In the absence of a fix for SERVER-4963, it would help with diagnosing balancer-out-of-window events if the pings stored in config.mongos included the mongos's local timezone next to the ping time. eg.

{ "_id" : "mongos1:27017", "ping" : ISODate("2015-06-01T07:09:12.708Z"), tz: "-0700", "up" : 986411, "waiting" : true, "mongoVersion" : "3.0.3" }