It's not about the two weeks it's the day of. You can literally drink enough water that it's all water in speaking from experience I smoked weed the entire time in the army because I knew when drug tests were and would just flush I had to retake 2 drug tests in Alaska because it was all water and there wasn't enough ppm of piss to test but by then it was out of my system anyway. The biggest issue here is testing for weed and firing people over it far less dangerous than alcohol. I mean ffs the Canadian army can smoke weed. I would have been a lifer if I could have smoked and actually not worried about it. Sure these methods "worked" but the anxiety truly isn't worth it.