[#111] Improve ephemeral message phrasing

[dcastro]

Description

Problem: For users in, let's say, Tallinn, the ephemeral message will say <time> <date> in Europe/Athens. Technically, Tallinn and Athens are on the same offset, but this message may be confusing for some users.

Solution: Amend the message to instead say <time> <date> in your timezone (Europe/Athens).

Related issue(s)

Fixed #111

:white_check_mark: Checklist for your Pull Request

Related changes (conditional)

• Tests

  • [x] If I added new functionality, I added tests covering it.
  • [x] If I fixed a bug, I added a regression test to prevent the bug from silently reappearing again.

• Documentation

  • [x] I checked whether I should update the docs and did so if necessary:
  • README
  • Haddock

Stylistic guide (mandatory)

• [x] My commits comply with the policy used in Serokell.
• [x] My code complies with the style guide.

✓ Release Checklist

• [ ] I updated the version number in package.yaml.
• [ ] (After merging) I created a new entry in the releases page, with a summary of all user-facing changes.
  • I made sure a tag was created using the format vX.Y