Dating events and objects is one of the most basic things a historian can do, but that does not mean it is simple. Radiocarbon dating offers no precise dates, but only a possibility that an object dates from a certain age. Dendrochronology is impossible if there is no tree ring sequence available for the area you are studying.
This means that the old methods of establishing a chronology have not been superseded. In turn, this means that unless something is dated according to the common, Christian era (or a similar era), you will have to make use of ancient lists of kings and magistrates.