##### SUMMARY

`ansible_date_time.tz` gives an invalid Timezone `CEST`.

In [lib/ansible/module_utils/facts/system/date_time.py, line 55](
https://github.com/ansible/ansible/blob/d3cab602a5b4578d5623bc5d4322681294abf2c2/lib/ansible/module_utils/facts/system/date_time.py#L55), `tz` should be assigned a valid Timezone name.

Actually it is assigned `time.strftime("%Z")`, which returns `CEST` when the current Timezone is `CET` and it is summer time.

It should be assigned `time.tzname[0]` (see [Python documentation](https://docs.python.org/3/library/time.html#time.tzname)).

Proposal :

```python
tz, _ = time.tzname
date_time_facts['tz'] = tz
```

References :

* https://en.wikipedia.org/wiki/List_of_tz_database_time_zones
* https://www.iana.org/time-zones
* `ls -l /usr/share/zoneinfo`
* `date`, executed on April 17, at 14:57 GMT (16:57 in Paris)  :
  * `TZ=Europe/Paris date` prints *Fri Apr 17 **16:57:03 CEST** 2020* 👍 
  * `TZ=CET date` prints *Fri Apr 17 **16:57:03 CEST** 2020* 👍 
  * `TZ=CEST date` prints *Fri Apr 17 **14:57:03 CEST** 2020* 👎 
  * `TZ=FOO date` prints *Fri Apr 17 14:57:03 **FOO** 2020* 👎 
##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME

facts

##### ANSIBLE VERSION

```
ansible 2.9.5
  config file = None
  configured module search path = [u'/home/ubuntu/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
  ansible python module location = /home/ubuntu/venv/local/lib/python2.7/site-packages/ansible
  executable location = /home/ubuntu/venv/bin/ansible
  python version = 2.7.17 (default, Nov  7 2019, 10:07:09) [GCC 7.4.0]
```

##### CONFIGURATION

N/A

##### OS / ENVIRONMENT

N/A


##### STEPS TO REPRODUCE

* Configure the target host Timezone to be `Europe/Paris`
* Set system time to sometime in the *summer*
* Run `ansible -m setup -a filter=ansible_date_time`

##### EXPECTED RESULTS

```
localhost | SUCCESS => {
    "ansible_facts": {
        "ansible_date_time": {
            ...
            "tz": "CET", 
            ...
        }
    }, 
    "changed": false
}
```

##### ACTUAL RESULTS

```
localhost | SUCCESS => {
    "ansible_facts": {
        "ansible_date_time": {
            ...
            "tz": "CEST", 
            ...
        }
    }, 
    "changed": false
}
```
#
#
#
#
from __future__ import (absolute_import, division, print_function)
__metaclass__ = type
import datetime
import time
from ansible.module_utils.facts.collector import BaseFactCollector
class DateTimeFactCollector(BaseFactCollector):