Why do imported photos have wrong time zone

have you been NYC when you import the photos from your iPhone?

Photos has to guess the correct time zone, because there is no standard tag for the timezone in the capture date.

On import Photos will just see 10:00 am or so in the capture time, but does not know, how the camera clock has been set when the photo has been taken. It will try to make a guess based on other data.

• If the photos are directly transferred by iCloud when you take them, the current camera timezone (the time zone of your iPhone) will be used to interpret the capture time.
• If the photo is tagged with GPS, the the timezone of the GPS location may be used, even if the camera or iPhone may still have been set to a different timezone. The clock in my cameras is always set tu UTC, wherever I am going, but this way I know exactly how the clock has been set.
• If the photos do not have GPS tags, because they have been taken inside building, for example, Photos will use the timezone of the system time of your Mac, when you import the photos to your Mac, or, if it is an iPhone, the timezone the iPhone is currently using.

You can batch correct the timezone for the photos taken with your wife's iPhone, if you collect her photos in an album or smart album and select them all at once, then use "Adjust Date&Time" and change the Time Zone strip and the "Closest City" in the panel. This will change the "Time Adjusted" Set that back, so that only the timezone will be changed , not the offset to "Original Time":

You're welcome, Dan. There is unfortunately no standard for the Timezone information for the capture date. It would help a lot, if it were. Or if Photos would at least be showing the timezone in the Info. I loved the way this has been handled in Aperture. When we imported photos to Aperture, We could tell Aperture the timezone the camera has been set to, when the photos have been taken, and we could tell Aperture, which timezone it should use to show the date and time in Aperture. That has been perfect.