The Y2K Readiness Commission will be "quietly monitoring" how computer systems cope with leap day today.
Technical adviser John Good says the commission expects some failures, but they are unlikely to affect essential services.
"The sectors themselves will be keeping an eye on it. We don't have a full-blown nationalmonitoring effort."
He said resources were put into monitoring the New Year rollover because of concern about control systems in essential services and the risk of public panic.
"What happened at New Year was it went quietly because the people had done the work [fixing non-compliant systems] and the gods were with us - the incidence of problems in control systems turned out, once we started looking, to be very low, so it all added up to a smooth transition."
The Y2K problem was related to some computer systems using two digits instead of four for the year, and being unable to read 00 as 2000.
The leap year problem is if programmers have failed to take into account 2000 being a leap year.
"Most people would have dealt with the leap year problem while they did their Y2K fixes.
"However, there is a risk some did not, and that some of the solutions may be based on a misunderstanding of the problem.
"Many people didn't get their heads around the Gregorian calendar, and the fact 1900 wasn't a leap year but 2000 was."
When the problem occurs could also depend on the coding. In 1996 Comalco's Tiwai Point and Tasmanian aluminium smelters crashed at midnight on December 30, 1996, because the control system failed to take into account the extra day during the year.
Mr Good said the commission was conducting a survey on whether companies had Y2K-related failures.
"It's anonymous, so people will answer honestly, going on our past surveys."
The commission will deliver a final report to Government at the end of March and then cease to exist.
There had been date-related failures, he said, "but all the firms involved have concealed them. Admitting they happened is like admitting your parentage wasn't legitimate."
