protected void setLastModified(long last_modified) {
        this.last_modified = last_modified;
    }
Sets last modified date of the chm file

@param last_modified
tika-parsers/tika-parsers-standard/tika-parsers-standard-modules/tika-parser-microsoft-module/src/main/java/org/apache/tika/parser/microsoft/chm/ChmItsfHeader.java