A method for encoding of media files to embed a data segment and time restriction information into the media file in order to restrict the time period when decoding and processing of the embedded data segment can be performed is described. The media file is capable of being decoded for playback as a media stream. It also includes a method for decoding the data segment as the encoded media file is reproduced as a media stream only during a specified time period as compared to the current time of day and/or date when the media stream is being played back. The restrictions preferably include a time tag specifying the start of a time period for reproducing the data segment or a time tag specifying the end of the time period, or both, in which case the time tags specify the start and end of the time period. The reproducing of the data segment includes subsequent processing for enabling the data to be displayed to a user. The method is capable of decoding previously encoded media files with embedded data for reproduction only during a predetermined time period specified by the corresponding time tags.