Relative dating stems from the idea that something is younger or older relative to something else.
When it comes to dating archaeological samples, several timescale problems arise.
One good example would be the elevated levels of Carbon-14 in our atmosphere since WWII as a result of atomic bombs testing.
Therefore, radiocarbon dates need to be calibrated with other dating techniques to ensure accuracy.
More recently is the radiocarbon date of 1950 AD or before present, BP.
There are two techniques for dating in archaeological sites: relative and absolute dating.
For example, Christian time counts the birth of Christ as the beginning, AD 1 (Anno Domini); everything that occurred before Christ is counted backwards from AD as BC (Before Christ).