Like most everyone else, Pentagon officials were nervous about how its computers would make the transition from 1999 to 2000.

A newly declassified report details how nervous they were — because most Defense Department computers were not ready for the new year.

But of course everyone knows those worries turned out to be unfounded; the transition came off without a glitch.

When the clocks strike midnight and the date changes, the Defense Department might be unprepared to meet the year 2000.

A 1998 study by the DoD IG found four out of five joint base operations centers still had some work to do in order to deal with Y2K.

The watchdog inspector general report was published in October 1998 but was considered sensitive due to the discussions about military computer systems.

IG spokeswoman Bridget Serchak confirmed the report was only made public this year, and posted to the investigative office's website in December.

When the calendar changes from 2015 to 2016, it's unlikely the Pentagon will have any issues. But back in the late 1990's, it was a great concern that the switch in date from 99 to 00 might cause all sorts of problems with computer systems.

Because the computers used a two-digit system for years, many experts were concerned that the 00 that represents 2000 could be indistinguishable from 1900.

The IG's audit reviewed the status of five joint centers and their compliance with a President William Clinton executive order "that no critical federal program experiences disruption because of the Y2K problem."

"Although they have made some progress to resolve potential Y2K problems, four of the five Joint Centers face a high risk that Y2K-related disruptions will impair mission capabilities," the IG report said.

At the time, the five joint centers were being shifted into U.S. Atlantic Command, which was dissolved in 1999, just a year after the report came out. Most of the units and capabilities were transferred into the new U.S. Joint Forces Command, which was itself closed in 2011.

The IG said the centers had taken several positive actions, including developing strategic plans and assembling specialist teams for taking on the Y2K challenge. Plus the centers were ensuring that any new software purchases or updates were Y2K compliant.

But the inspector general also found that of 100 mission-critical systems spread between the five joint centers, officials had not evaluated whether 56 were ready to meet the change in date.

"The Joint Centers need to fully determine the Y2K compliance status for all mission-critical systems to ensure that the warfighting mission will not be adversely affected," the IG said.

Of those they had assessed, 25 were ready to meet the new year, but 19 were not. The watchdog office was also concerned with how the centers were documenting Y2K preparedness, and noted that "mission-critical systems may unexpectedly fail because they were identified as compliant without being validated."

The IG also noted that the centers did not have contingency plans in place — just in case everything did go wrong on New Year's Eve — and needed to craft ideas by the Pentagon-mandated deadline of Dec. 31, 1998.

"With less than three months remaining, the Joint Centers must take a more aggressive approach to resolve potential Y2K computing problems," the report said. "Unless further progress is made, the Joint Centers' ability to facilitate or participate in Joint Service warfighting exercises may be impacted."

Only the Joint Battle Center in Suffolk, Va., largely got a pass, with investigators noting it had "a commendable Y2K program in place."

The other four centers were the Joint Command and Control Warfare Center at Kelly Air Force Base, Texas; Joint Communications Support Element in Tampa, Fla.; Joint Warfare Analysis Center in Dahlgren, Va.; and the Joint Warfighting Center in Fort Monroe, Va.

Of course, on Jan.1, 2000, the digital apocalypse that some had feared never came to pass, and the Defense Department computer systems had no major issues.

Now the Pentagon has only 84 more years to prepare for 2099.