Where Is It?
The During block is found in the Events drawer of the Blawx toolbox.
What Does It Do?
The During block is used to query what periods of time a statement was true. It accepts two datetimes and a statement. If the times are variables, and the statement is specified, it will find the times at which that statement began to hold, and stopped holding. That is to say, it returns only the start and end points that are the most extreme for the duration that the statement was true.
Because of this it cannot be used to check whether or not something held for the entirety of a duration. If something is true from date 1 to date 5, and you use the during block to check if it was true from date 2 to date 4, the during block will return false, because it returns only the widest possible durations.
The during block is a statement block and can be stacked with other statement blocks.
The during block is capable of reporting that a statement held from the beginning of time, or until the end of time. But in order to take advantage of that capability, you must have specified the initial and ultimate values of that statement using the initially and ultimately blocks.