Why a night shift can be 13 hours

A 19:00–07:00 night is twelve hours on most days. On the night the clocks go back it is thirteen real hours, and on the night they go forward it is eleven.

We count the real elapsed time, so the night somebody actually worked thirteen hours is exported as thirteen. Systems that subtract one clock face from another short that nurse an hour of pay every autumn.

The authority is the place the work happens: the site's timezone, or the facility's if the shift is call carried somewhere you do not operate. Not the server's, and not yours.