Daylight savings time is moving earlier in the US and some other countries, proving a headache for IT professionals and businesses.
With less than a year to fix calendars and timers, it's been a struggle to get it done on time for this weekend's time shift.
Many computers and electronic devices haven't been automatically updated because they can't be; this means that people who rely on electronic calendars and reminders may find themselves in a bit of a muddle.
An insider told Pocket-lint, "With Y2K we had five years to plan and get it fixed. With this, we've had just 11 months".
Banks who haven't had their systems fixed may make late payments, while travel companies may have trouble with arrival and departure times.
Microsoft released a Windows update back in November that should prompt the operating system to change automatically; patches are also available for manual download.
Whatever problems do occur should right themselves three weeks after the shift, at the time when the change usually occurs.