gulp-stamp is a gulp plugin to add stamp in head of js/css files if they were changed.

usage

var gulp = require('gulp');
var uglify = require('gulp-uglify');
var stamp = require('gulp-stamp');
var moment = require('moment');

gulp.task('scripts', function () {
    var time_stamp = '/* ' + moment().format('YYYY-MM-DD HH:mm:ss') + ' */\n';
    gulp.src(['src/**/*.js'])
        .pipe(uglify())
        .pipe(stamp('build/', time_stamp))
        .pipe(gulp.dest('build/'))
});