1 If I create a file in Linux (SuSE xfce) at time=t, then copy and paste it into onto my Jolla C (18.104.22.168) connected via MTP (mtp://[usb:001,006]/Mass storage/...) it displays the timestamp as t-1 hour (which happens to be the UT time here in the UK at the moment). The same file in the File Browser on the Jolla C correctly displays time=t. So that's OK.
2 A file created on the Jolla at time=t displays in the MTP window on Linux as time t-1 - and retains that time if copy+pasted into a Linux directory. That's not OK.
3 If the file created in Linux, as in 1, is copied straight back to another directory in Linux, its timestamp is t-1.