TZAG plugin
Timezone Appropriate Greeting.
List of timezones (wrt UT) with the greetings for each one.
Example at 12:00 UT:
UT-8 - UT+0: Good morning
UT+0 - UT+6: Good afternoon
UT+6 - UT+9: Good evening
Other timezones: Good night
Morning being after 04:00, afternoon after 12:00, evening 18:00, night starting at 21:00.