When I worked at Cerner years ago (now owned by Oracle), there were rumors that the Cerner EMR still could barely handle DST* spring forward, but could not handle DST fall back (where the 01:00 hour is repeated) -- you had do preemptively switch to pen-and-paper for the hours around the switch. I assume this was because someone back in the initial database design used local time instead of UTC for some critical patient-care timestamp fields in the database, and then had a bear of a time getting reliable times out of the database during the witching hour.

* Daylight Saving Time in the USA. And yes, everyone in the USA changes non-networked clocks twice a year because of some "brilliant idea" someone shoved through Congress in 1974.

EDIT: I wonder if Cerner finally fixed it?