gistfile1.yml

---
- name: Group by Distribution
  hosts: all
  tasks:
    - group_by: key={{ansible_distribution}}

- name: Set Time Zone
  hosts: Ubuntu
  gather_facts: False
  vars:
  - my_zone: 'America/New_York'

  tasks:
    - name: check current timezone
      shell: cat /etc/timezone
      register: current_zone
      changed_when: False

    - name: Set timezone variables
      copy: content={{my_zone}}
            dest=/etc/timezone
            owner=root
            group=root
            mode=0644
            backup=yes
      when: current_zone.stdout != my_zone
      notify:
        - update timezone
  handlers:
    - name: update timezone
      command: dpkg-reconfigure --frontend noninteractive tzdata

Added 'changed_when' to prevent the 'check current timezone' task from returning a 'Changed' status on all runs. (requires Ansible 1.3+)