They fear the four identical figures in today's date could cause problems. Warehouses could see an unexpected bulge in orders and ships' navigation systems could be affected.
The potential problem relates to computer-based systems that require all the date fields to be filled in. When staff do not have all the necessary information they tend to enter dates such as 9/9/99, which are quick and easy to key in.
Tony Stock, the operations director of Action 2000, said: "It might arise in a situation where there's an order without a delivery date, and the person putting in the data just puts 9/9/99 to get the machine to accept it."
The problem will then be sorting out such "ghost" entries from the real orders due today. "It's a user-generated problem ... The programmers could not have predicted it," he said.
Meanwhile, in Stornaway, in the Western Isles, the Anglian Prince, an emergency tug, was brought into service yesterday - three weeks early - in case it is needed to rescue ships affected by computer problems caused by today's unusual date. Similar tugs also went into winter service early at Falmouth and Dover.
A Maritime and Coastguard Agency spokesman said computer problems today could result in ships "losing power or steering, or the malfunction of navigational equipment".
Computer programs written about 30 years ago often used "9999" to indicate the end of a file. If such systems are still in use today, computers relying on them might grind to a halt.
However, Mr Stock thought widespread problems were unlikely. "We have only identified one such case of that happening in Britain, with a vibration monitoring system for rail tracks. That was found about two years ago and all the models have been replaced," he said.Reuse content