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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

- Attached files will have their content-type set to C(application/octet-stream).
    type: list
    default: []
    version_added: '1.0'
  headers:
    description:
    - A list of headers which should be added to the message.
    - Each individual header is specified as C(header=value) (see example below).
    type: list
    default: []
    version_added: '1.0'
  charset:
    description:
    - The character set of email being sent.
    type: str
    default: utf-8
  subtype:
    description:
    - The minor mime type, can be either C(plain) or C(html).
    - The major type is always C(text).
    type: str
    choices: [ html, plain ]
    default: plain
    version_added: '2.0'
  secure:
    description:
    - If C(always), the connection will only send email if the connection is Encrypted.
      If the server doesn't accept the encrypted connection it will fail.
    - If C(try), the connection will attempt to setup a secure SSL/TLS session, before trying to send.
    - If C(never), the connection will not attempt to setup a secure SSL/TLS session, before sending