Cannot write GPSTimeStamp properly in ExifInterface

Question

I'm trying to write that property as exif data using exif interface, but the exif reader I'm using never recognizes the defined data.

I've tried it with things like the following:

exif.setAttribute("GPSTimeStamp", "((15, 1), (32, 1), (7, 1))"); 

exif.setAttribute("GPSTimeStamp", "(15, 1), (32, 1), (7, 1)"); 

exif.setAttribute("GPSTimeStamp", "15/1,32/1,7/1"); 

But none of them are working, and I don't see any other suitable format.

Which would be the correct format to set GPSTimeStamp?