Information encryption has become increasingly important in recent years; however, information encryption materials, especially those encrypting on a time scale, are still in fancy. Herein, a “time‐lock” information encryption material is developed based on a time‐dependent fluorescent hydrogel. The fluorescence color of this hydrogel can be regulated between green and yellow, with distinctive changes in intensity, on a time scale by controlling the concentration of urea/urease and HCl. By taking advantage of this feature, “time‐locked” information can be encoded. Such information self‐erases with time, and moreover, fake or even opposing information is generated during this process. The correct information can only be recognized at a specified time, i.e., using a “time‐key” to decrypt the information. This time‐dependent feature endows the material with a higher level of security and provides new insight for information encryption. A time‐dependent fluorescent hydrogel driven by the hydrolysis of urea is developed to achieve information encryption. Information is encoded in this material that self‐erased with time, and moreover, false information is generated during the erasing process. The correct information can only be recognized at a specific time.