Timezone CET/UTC not handled correct

[pjw65]

The following code (on Ubuntu Linux 24.01 shows, that CET (UTC+1) is not correct handled, the UTC time differs by 2 hours instead of 1. CEST (Summer time) differs by 3 instead of 2 hours!
Local sunrise time seems correct,

export TZ="Europe/Zurich"; Zurich="47.3774121N 8.4541624E"; ./sunwait list rise $Zurich; ./sunwait list rise gmt $Zurich; date; date -u
07:05
05:05
Do 31 Okt 2024 07:06:18 CET
Do 31 Okt 2024 06:06:18 UTC

same with "debug" parameter added:

Debug: argv[1]: >list<
Debug: argv[2]: >debug<
Debug: argv[3]: >rise<
Debug: argv[4]: >47.3774121n<
Debug: argv[5]: >8.4541624e<
Debug: All output to use local timezone (nogmt).
Debug: Now   utcTm:  Thu Oct 31 16:20:23 2024 GMT
Debug: Now localTm:  Thu Oct 31 17:20:23 2024 CET
Debug: Now UTC bias (add to GMT to get CET) hours: 1.000000
Debug: UTC Bias (hours): 1.000000
Debug: Now: Days since 2000: 9070
Debug: Target  year set to: 124
Debug: Target   mon set to: 9
Debug: Target  mday set to: 31
Debug: Target   utcTm:  Thu Oct 31 00:00:00 2024 GMT
Debug: Target localTm:  Thu Oct 31 01:00:00 2024 CET
Debug: Target UTC bias (add to GMT to get CET) hours: 1.000000
Debug: Target: Days since 2000: 9070
Debug: Co-ordinates -  Latitude: 47.377412N
Debug: Co-ordinates - Longitude: 8.454162E
Debug: Twilight - Daylight
Debug: User specified offset (hours): 0.000000
Debug: Function selected: List
Debug: sunriset.c: Sun directly south: 11.164019 UTC, Diurnal Arc = 10.155840 hours
Debug: sunriset.c: Days since 2000: 9070
07:05
Debug: argv[1]: >list<
Debug: argv[2]: >rise<
Debug: argv[3]: >debug<
Debug: argv[4]: >gmt<
Debug: argv[5]: >47.3774121n<
Debug: argv[6]: >8.4541624e<
Debug: All output to use UTC.
Debug: Now   utcTm:  Thu Oct 31 16:20:23 2024 GMT
Debug: Now localTm:  Thu Oct 31 17:20:23 2024 CET
Debug: Now UTC bias (add to GMT to get CET) hours: 1.000000
Debug: UTC Bias (hours): 1.000000
Debug: Now: Days since 2000: 9070
Debug: Target  year set to: 124
Debug: Target   mon set to: 9
Debug: Target  mday set to: 31
Debug: Target   utcTm:  Thu Oct 31 00:00:00 2024 GMT
Debug: Target localTm:  Thu Oct 31 01:00:00 2024 CET
Debug: Target UTC bias (add to GMT to get CET) hours: 1.000000
Debug: Target: Days since 2000: 9070
Debug: Co-ordinates -  Latitude: 47.377412N
Debug: Co-ordinates - Longitude: 8.454162E
Debug: Twilight - Daylight
Debug: User specified offset (hours): 0.000000
Debug: Function selected: List
Debug: sunriset.c: Sun directly south: 11.164019 UTC, Diurnal Arc = 10.155840 hours
Debug: sunriset.c: Days since 2000: 9070
05:05