Combine peaches and sugar in a bowl. Mix well and let stand, stirring occasionally, for 10 minutes. Stir pectin into lemon juice in a small bowl. Add pectin mixture to the peaches. Stir jam constantly until sugar is completely dissolved and no longer grainy, about 3 minutes.
Pour jam into food storage containers, leaving 1/2 inch space at the top for expansion during freezing. Cover and let stand at room temperature until set, about 24 hours. Refrigerate for up to 3 weeks or in the freezer for up to 1 year. Thaw in refrigerator.