PURPOSE: To enable to display the elapsed time with color change, by using a composition in which color material changing its color reversibly through oxidation and reducing reaction and a reducing substance are contained essentially.

CONSTITUTION: As a color material reversibly changing its color by oxidation and reduction, in addition to safranine T, phenosafranine, methylen blue and the like which are generally called as oxidation/reduction indicators, those can all be used if they change reversibly the color due to oxidation and reduction reaction among thiazine dye, oxazine dye, and azide dye and the like, and as a reduction substance, it can be that which has an ability to reduce the color substance in combination with said color substances. As the form of display substance of elapsed time, it is possible as powder shape of constituent, tablet, printed with ink and paste with water or solvent into a tube.