Alternative time zone databases

[Mathieu Decaffmeyer]

Thank you for this great library 👍

The Readme says tzdata library is recommended, however it is the most bugged time zone database at present. See https://elixirforum.com/t/29358
It also crashes the application for some datetimes.

Two bug-free time zone libraries are:

• https://github.com/mathieuprog/tz (mine)
• https://github.com/hrzndhrn/time_zone_info

[Tomek Zawadzki]

Hello! We use tzdata only as optional dependency for local testing. The library itself does not depend on any specific time zone database. If you think that these unit tests would benefit from upgrading to an alternative time zone database, feel free to submit a PR 😄