Clocks across the country have been the victim of a wind-up by European legislation dictating the end of British summertime.
Almost 2,000 clocks made by Smith of Derby - one of Britain's best-known clock makers - have gone back an hour seven days early.
The problem affects clocks in town centres, supermarkets and businesses controlled by a microchip that changes the time automatically.
The chips, in use since 1999, were supposed to run for almost 100 years.
They were supposed to turn back the clocks on the fourth Sunday of October - a British tradition.
But they have been rendered useless by EU legislation, which says all members of the European Union must put their clocks back on the last Sunday of October.
Baffled people in Darlington noticed the clocks in the tower on High Row, Morrison's on North Road, and at funeral directors Seaton Leng and Sons, in Bondgate, were an hour behind.
Many people thought they had forgotten to put their clocks back and were running an hour earlier than intended.
Smith of Derby has been making timepieces since 1736, but only those manufactured between 1999 and 2002 have been affected.
Managing director and chairman Peter Sully said: "We knew there had been discussions between EU countries but we failed to pick up on the fact that a decision had been made."
The firm is in talks with its customers, including Darlington Borough Council, to decide whether a temporary or permanent solution is the best way forward.
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