How can I find Time Zone Database version when using `arrow` or `dateutil`?
Question: I am using `arrow` module for Python for time zone manipulations. As far as I
understand it, it relies on `dateutil` module for time zone information.
`dateutil` claims:

> Internal up-to-date world timezone information based on Olson's database.

I have only found `c:\Python34\Lib\site-packages\dateutil\zoneinfo\dateutil-
zoneinfo.tar.gz` which seems to be used. I have deducted that it is downloaded
from <http://www.iana.org/time-zones>, however it still does not give any
hints what version of the database it is.

Is there a way to find what version of Olson's database is being used by
`arrow` module?


Answer: Yes, arrow depends on dateutil for tz data.

Unfortunately, dateutil doesn't keep the tzdb version number when it builds
its data file, so it is not available at run time.

Walking through [the dateutil source
code](https://github.com/dateutil/dateutil):

  * The version number can be seen in `tzdata_file` in [zonefile_metadata.json](https://github.com/dateutil/dateutil/blob/master/zonefile_metadata.json).

  * In [updatezinfo.py](https://github.com/dateutil/dateutil/blob/master/updatezinfo.py), the filename is passed from the metadata into the `rebuild` function,

  * In [the `rebuild` function](https://github.com/dateutil/dateutil/blob/2.4.0/dateutil/zoneinfo/__init__.py#L79-L108), you can see that the data from the file is loaded, but the filename itself is not retained, nor is the `VERSION` constant read from [the tzdata makefile](https://github.com/eggert/tz/blob/master/Makefile#L8).

If this feature is important to you, I suggest opening a feature request in
[the dateutil issue tracker](https://github.com/dateutil/dateutil/issues).

