Date is a Java class that can represent a timestamp.
The example shown below will give you a good idea of how it works :
%tc = Complete date and time
%tr = just the time
%tA = Day of the week
%tB = Month
%td = day
< is just another flag in the format specifier that tells the formatter to "use the previous argument again." It saves you from retyping the arguments.
Check out the API for Date class. Click here to see.