A method and 
system for modifying 
computer program logic with respect to a predetermined aspect, comprising (a) before run time: analyzing compiled 
computer program logic of a module for processes involving the predetermined aspect before run time, substantially without decompilation or reference to 
computer program source code; and storing a set of modifications relating to computer 
program logic modifications of the module relating to the predetermined aspect; and (b) at run time: based on the stored set of modifications, selectively transferring 
program control from the module to a separate logical structure, executing modified 
logical operations with respect to the predetermined aspect, and subsequently returning 
program control to the module. The predetermined aspect may be, for example, a 
data type, 
algorithm type, or interface specification. In a preferred embodiment, the predetermined aspect is date related data, and more particularly, to 
logical operations relating to date related data which are flawed. The 
system preferably operates in a mainframe environment, wherein the compiled computer program constitutes one or more load modules, executing under an 
operating system, wherein the computer 
program logic modifications preferably comprise program flow control diversions in an original object module, which selectively transfer logical control to a separate object module to effect modifications to the computer 
program logic, followed by a return of control to the original object module.