This thesis deals with different ways of how to safely time-stamp digital content. The need for time-stamping arises when we would like to create evidence that certain content existed (or that a certain person was present somewhere) in a precisely specified period of time, so that later we can refer to this evidence. Creating temporal order in the digital world can prove to be difficult, since no data, including time, is recorded permanently. The
system clock, which measures time with the help of an oscillator, can easily be manipulated. Who to trust in such case? Specialized services, which time-stamp data with a reliable temporal accuracy, can be found online. Our study includes an analysis of known trust based schemes as well as the implementation of time-stamping service which uses various techniques to prove the placement of data within a specified time period.