generate APK as per your required name

apk_name

  buildTypes {
        debug {

applicationVariants.all { variant ->
                variant.outputs.each { output ->
                    def date = new Date();
                    def formattedDate = date.format('dd-MM-yyyy')
                    output.outputFile = new File(output.outputFile.parent,
                            output.outputFile.name.replace("-release", "-release_" + formattedDate)
                            //for Debug use output.outputFile = new File(output.outputFile.parent,
                            //                             output.outputFile.name.replace("-debug", "-" + formattedDate)
                    )
                }
            }
     }
     }