Dear Alexander, while searching for a portable way to get the gmt offset I have found out that your patches set the wrong semi-octet to de/encode the sign. 3GPP TS 03.40 ch. 9.2.3.11 specifies that "bit 3 of the seventh octet of the TP-Service-Centre-Time-Stamp field [...] represents the algebraic sign of this difference." This is because the more significant digit is encoded in bits 0-3. Currently a two hour time offset (8*15min) will beencoded as 0x80 which will be decoded as -0. Please take a look at my two patches and squash them into yours. [FIX 1/2] fixup! sms: Fix gsm340_scts() to correctly decode absolute [FIX 2/2] fixup! sms: Fix support of negative timezone offsets in Regards, Daniel