http://stackoverflow.com/questions/10314343/schedule-fortnightly-jobs-on-jenkins

ability to provide scheduler that runs a build in fortnightly.
It could be done by using "#" symbol but it will fail in case of months having 3 build days. Eg you want to schedule for every fortnight starting coming Monday at mid night but in case there are 5 Mondays in a month than it will fail.

We can do it by calculating if week in even number or odd. That will be consistent for one year atleast.