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##### SUMMARY
mail module does not send email with Date header. It should send email with "Date" header automatically without any manual email header manipulation.

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
mail

##### ANSIBLE VERSION
```
ansible 2.8.1
  config file = /etc/ansible/ansible.cfg
  configured module search path = [u'/home/yclee/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/lib/python2.7/dist-packages/ansible
  executable location = /usr/bin/ansible
  python version = 2.7.15+ (default, Nov 27 2018, 23:36:35) [GCC 7.3.0]
```

##### CONFIGURATION
(None)

##### OS / ENVIRONMENT
Ubuntu 18.04

##### STEPS TO REPRODUCE
N/A

##### EXPECTED RESULTS
email should have Date headers

##### ACTUAL RESULTS
email did not  have Date headers and I have to manually insert it

host: 127.0.0.1
    port: 2025
    subject: Ansible-report
    body: Hello, this is an e-mail. I hope you like it ;-)
    from: jane@example.net (Jane Jolie)
    to:
    - John Doe <j.d@example.org>
    - Suzie Something <sue@example.com>
    cc: Charlie Root <root@localhost>
    attach:
    - /etc/group
    - /tmp/avatar2.png
    headers:
    - Reply-To=john@example.com
    - X-Special="Something or other"
    charset: us-ascii
  delegate_to: localhost
- name: Sending an e-mail using the remote machine, not the Ansible controller node
  mail:
    host: localhost
    port: 25
    to: John Smith <john.smith@example.com>
    subject: Ansible-report
    body: System {{ ansible_hostname }} has been successfully provisioned.
- name: Sending an e-mail using Legacy SSL to the remote machine
  mail:
    host: localhost
    port: 25
    to: John Smith <john.smith@example.com>
    subject: Ansible-report