I smoked a gram of weed lastnight for the first time in 3 months. Can I get it outta my system in 19 days?

Maybe, maybe not. Studies find that marijuana can be detected in the blood up to 3 weeks, and in the urine up to 3 months, depending on the person, the amount used, and his frequency of smoking mj. In frequent users, mj is detectable for a long time. With infrequent, occasional users, mj may be out of the body after a few days in some instances. Mj brownies are probably detectable for similar durations as smoking.
Nothing more to do . Once you have smoked marijuana, there is nothing you can do, eat, or drink that would get it out of your system more quickly. Routine drug testing can detect marijuana 1-3 weeks after using.