The correct handling of numerical ages and their standard deviations and a proper introduction to error propagation or propagation of uncertainty and statistical evaluation are important to avoid misleading chronological conclusions and statements even though based on properly determined and reliable numerical dates. The conclusions may also be erroneous if dates were taken from databases without sufficient background information on the origin of the dated material and the applied analytical techniques. This paper is an introduction into the field of mathematical handling and testing of numerical ages. The most common and simple calculations and statistical tests that are needed are described and the steps involved are demonstrated on examples. The problems involved in the visualization of numerical dates in the form of normal histograms and dispersion histograms are discussed.