Global_Version

All libraries have a certain version. This version can be seen in the PLC library repository among others.
A global constant contains the library version information (of type ST_LibVersion):

Global_Version

VAR_GLOBAL CONSTANT
    stLibVersion_Tc3_EventLogger : ST_LibVersion;
END_VAR

To check whether the version you have is the version you need, use the function F_CmpLibVersion (defined in the Tc2_System library).