I have a field with numbers in it (concentration of chemical compounds that were presented in aquatic environments) and I'd like to combine them with a field which would have date type capabilities but as a unique year (e.g. 2013, 2008 etc.) instead of a whole date (2/5/2013, 5/8/2008 etc.).
The year data represent the years of chemical analysis of water samples.
The general concept of this work is to provide me finally the information of the concentration and the year of analysis of a certain compound.
Also I'd like to have the ability to select concentrations by year.
For example: before the year of 2004 what was the concentrations of these substances?
How can I achieve the above?