The "timestamp" element in XML configuration files is quite useful. The same is true for the "define" XML element to dynamically define property values. Maybe it's worth to add some cross references between the timestamp documentation and the define-properties documentation, because the timestamp element can effectively be expressed with the property-define feature.

Obviously we need an appropriate PropertyDefiner implementation for this (which is quite trivial), so maybe you can add this to the logback distribution as well.

Obviously this improvement request has only limited use, but some purists like me don't like the idea that there is a "generic way" to do something (the property-define mechanism), and on top of this there is a second way to realize one special instance of this "generic way" (the dedicated "timestamp" XML element, which only wraps a slightly more complex "define" XML element).