@Override
        protected String fill(String pattern, long timeMillis, int logLevel, String tag, String message) {
            return pattern.replace(wrappedParameter, threadLocalDateFormat.get().format(new Date(timeMillis)));
        }
Fill the original pattern string with formatted date string.
android/android_framework/base/src/main/java/com/elvishew/xlog/flattener/PatternFlattener.java