Here’s a date the terminally inept Lower Manhattan Development Corp. needs to mark on its calendar:

Jan. 18, 2011.

That’s when the trial starts for three contractors accused of manslaughter in the 2007 Deutsche Bank building blaze that killed two city firefighters.

If the remnants of that 41-story tower — shattered by debris on 9/11 — are still standing in January, it will mark yet another historic failure for the LMDC.

Yesterday, a state Supreme Court justice sustained manslaughter charges against the contractors, who cut up a basement standpipe meant to provide water to the site in case of a fire.

When a worker’s cigarette torched the building, it took an hour for water to start flowing as 100 firefighters swarmed the perilous blaze. Two suffocated in a maze of blocked exits and sealed-off stairways on the 14th floor.

The contractors weren’t alone in their malfeasance. The Fire Department skipped inspections and had no plan for tackling the building.

Still, the tower shouldn’t have been there at all.

Thanks to the LMDC’s bungling, 26 floors were still standing at the time of the fire. And it’s been another three years, and the building is still there.

LMDC officials first said it would be torn down in 2007. Wrong.

The finish line was then moved back to December ’08.

Then to August ’09.

Then to January ’10.

Now, an LMDC spokesman promises, just six stories remain and the building will be gone by the end of 2010.

The LMDC owes the city that much — and firefighters deserve to see it torn down before the trial starts in January.

Believe it when you see it.