Brought to my attention

Files on a PC have a time stamp: the date & time from when a file was created or when it was last modified.
    Whenever I compared a directory on a PC with the backup versions on a flash drive, everything was identical up to last Sunday, when the clocks went forward an hour to BST.
    But suddenly, the creation time of every file on the PC was an hour later than the backup – going back to when BST ended last year on Sunday October 31st. Before that, everything matched. Weird.