If you do not want to process the jam in a boiling-water bath, simply store it in the refrigerator for up to 2 months.
Combine rhubarb, sugar and orange zest in mixing bowl. Cover with plastic wrap, and refrigerate for 12 hours.
Strain liquid from rhubarb mixture into a large heavy saucepan, pressing on solids to release all juice. Set rhubarb aside.
Bring liquid to a boil, and cook over medium heat until syrupy and reduced by half, for 15 to 20 minutes, watching closely toward end to prevent scorching. Add reserved rhubarb and crystallized ginger, and cook, stirring, until rhubarb is soft and mixture has thickened, for about 5 minutes.
Pour into hot, sterilized half-pint jars, leaving 1DA4-inch headspace. Tighten lids, and process in a boiling-water bath for 10 minutes. Remove from heat, cool and store.