A time indicator that provides a color indicia after a predetermined period of time has passed after activation. The time indicator includes a substrate, e.g., a clear or transparent substrate, having an upper surface and a lower surface and a first portion and a second portion joined at a fold line. The first portion is of a smaller area than the second portion. An adhesive coats the upper surface of at least the second portion of the substrate. A first reactant is adhered to the upper surface of the first portion of the substrate and a second reactant is adhered to the upper surface of the second portion of the substrate. When the first portion is folded along the fold line so that the upper surfaces of the substrate contact each other, a portion of the adhesive on the second portion remains exposed. This exposed area may be used to attach the indicator to an article or documents. When so folded the first reactant and second reactant contact each other to activate the indicator and to provide the color indicia after the predetermined period of time after activation passes. In one embodiment, the indicator is used to detect the presence of a chemical residue, e.g., explosive compound residues.