yes, you are right. It is recorded in Z time as most (all?) Garmins do. There is a little symbol in the maps view for a drop down menu that allows to change the time zone of the gps track. Unfortunately my Garmin interrups the track file if connection is lost so I have to change each and every portion of the track. Might be easier to temporarily shift the pictures to a fake Z-time and back.
the dates in Aperture are very elaborate and involved.
- The tracks from Garmin or AMOD loggers - at least all that I have used - record tracks in UTC.
- Aperture imports images and interprets the capture dates with respect to the Timezone set in the System preferences. You can tell Aperture the correct timezone of your image capture time in the imprt settings: Camera time (the time the camera was set to) and actual time (the time zone you want o choose).
- Independently of what the capture timezone is set to, will Aperture show the capture time in the timezone of the image, but the "Date" field will show the date transformed to the system time zone, also the dates on the GPS tracks will be shown in system time, even if you corrected the time of the track and set it to UTC, for example.
You can see the time zones in the inspector, if you edit the Language&Text Preferences for the times as a custom setting, to show the time zones for the middle and long formats.
I keep all cameras set to UTC, so I no longer have to worry about consistency with tracks.
But if you use the Places view and find UTC dates irritating, the safest way would be to identify one image location that you are sure of and to drag it to the right location on the track. All other selected images will be assigned correctly.