The armed forces are still not fully millennium bug compliant.
The Ministry of Defence is not covered by the Action 2000 independent assessment, but says it has fixed 97% of its critical computer systems. It has set a target of full compliance by the end of the year.
According to the MoD, all Royal Air Force aircraft, Royal Navy ships and submarines and all weapons systems are ready for the year 2000.
The Ministry of Defence is confident that the UK's nuclear weapons are secure and say there is no risk of an accidental missile launch or nuclear weapons accident.
The MoD says it is working on contingency plans to make sure defence systems continue to work during and after the millennium period.
But the ministry's preparations have come in for criticism over the last few months.
In June, Commons Leader Margaret Beckett gave her quarterly report to MPs and singled out the MoD for failing to guarantee full compliance by December.
Later in the month, independent auditors checked a random sample of reportedly 'bug-free' defence systems as part of an ongoing audit due to be completed in the autumn. Some 15% had severe problems and 20% had minor glitches.
The MoD said the problems were being tackled and the systems did not involve nuclear weapons or other critical equipment.
The auditors also found problems with getting Y2K guarantees from military suppliers.
Watching the weather
Much of the work of the Ministry of Defence relies on public telecommunications services and electricity, though many areas do have back-up systems and generators.
But one thing more difficult to control is the weather. UK defence systems need accurate weather reports and the MoD has been overseeing Y2K plans at the Meteorological Office.
In the Action 2000 traffic light system, The Met Office's UK work was rated Blue in October, following an Amber rating in July. But the independent report did not cover weather forecasting worldwide and there is a risk that data from some countries could be disrupted.
Ministry of Defence Year 2000 programme
The Action 2000 traffic light codes:
Blue: The assessment has not identified any risks of material disruption to the infrastructure process.
Amber: The assessment indicates that there is some risk of material disruption to infrastructure processes, but that there is an agreed containment plan to rectify shortcomings.
Red: The assessment indicates that there is a severe risk of material disruption to infrastructure processes and that timely rectification might not be possible.