[PATCH 6/6] sms: Fix gsm340_scts() to correctly decode absolute valid times.

[Alexander Chemeris]

- Support negative timezone offsets decoding.
- Correctly account timezone offset and artificial offset mktime()
introduces.


-- 
Regards,
Alexander Chemeris.
CEO, Fairwaves, Inc. / ООО УмРадио
https://fairwaves.co