JavaScript
取得时间戳Math.round(new Date() / 1000)

//js获取当前时间戳的方法
var timestamp1 = Date.parse(new Date());
var timestamp2 = (new Date()).valueOf();
var timestamp3 = new Date().getTime();

//调用方法 能够很方便的将时间戳转换成日期的格式，如：
date('Y-m-d','1350052653');//很方便的将时间戳转换成了2012-10-11 
date('Y-m-d H:i:s','1350052653');//得到的结果是2012-10-12 22:37:33

封装的时间格式器

/** 
 * 和PHP一样的时间戳格式化函数 
 * @param {string} format 格式 
 * @param {int} timestamp 要格式化的时间 默认为当前时间 
 * @return {string}   格式化的时间字符串 
 */
function date(format, timestamp){ 
 var a, jsdate=((timestamp) ? new Date(timestamp*1000) : new Date()); 
 var pad = function(n, c){ 
  if((n = n + "").length < c){ 
   return new Array(++c - n.length).join("0") + n; 
  } else { 
   return n; 
  } 
 }; 
 var txt_weekdays = ["Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"]; 
 var txt_ordin = {1:"st", 2:"nd", 3:"rd", 21:"st", 22:"nd", 23:"rd", 31:"st"}; 
 var txt_months = ["", "January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"]; 
 var f = { 
  // Day 
  d: function(){return pad(f.j(), 2)}, 
  D: function(){return f.l().substr(0,3)}, 
  j: function(){return jsdate.getDate()}, 
  l: function(){return txt_weekdays[f.w()]}, 
  N: function(){return f.w() + 1}, 
  S: function(){return txt_ordin[f.j()] ? txt_ordin[f.j()] : 'th'}, 
  w: function(){return jsdate.getDay()}, 
  z: function(){return (jsdate - new Date(jsdate.getFullYear() + "/1/1")) / 864e5 >> 0}, 
   
  // Week 
  W: function(){ 
   var a = f.z(), b = 364 + f.L() - a; 
   var nd2, nd = (new Date(jsdate.getFullYear() + "/1/1").getDay() || 7) - 1; 
   if(b <= 2 && ((jsdate.getDay() || 7) - 1) <= 2 - b){ 
    return 1; 
   } else{ 
    if(a <= 2 && nd >= 4 && a >= (6 - nd)){ 
     nd2 = new Date(jsdate.getFullYear() - 1 + "/12/31"); 
     return date("W", Math.round(nd2.getTime()/1000)); 
    } else{ 
     return (1 + (nd <= 3 ? ((a + nd) / 7) : (a - (7 - nd)) / 7) >> 0); 
    } 
   } 
  }, 
   
  // Month 
  F: function(){return txt_months[f.n()]}, 
  m: function(){return pad(f.n(), 2)}, 
  M: function(){return f.F().substr(0,3)}, 
  n: function(){return jsdate.getMonth() + 1}, 
  t: function(){ 
   var n; 
   if( (n = jsdate.getMonth() + 1) == 2 ){ 
    return 28 + f.L(); 
   } else{ 
    if( n & 1 && n < 8 || !(n & 1) && n > 7 ){ 
     return 31; 
    } else{ 
     return 30; 
    } 
   } 
  }, 
   
  // Year 
  L: function(){var y = f.Y();return (!(y & 3) && (y % 1e2 || !(y % 4e2))) ? 1 : 0}, 
  //o not supported yet 
  Y: function(){return jsdate.getFullYear()}, 
  y: function(){return (jsdate.getFullYear() + "").slice(2)}, 
   
  // Time 
  a: function(){return jsdate.getHours() > 11 ? "pm" : "am"}, 
  A: function(){return f.a().toUpperCase()}, 
  B: function(){ 
   // peter paul koch: 
   var off = (jsdate.getTimezoneOffset() + 60)*60; 
   var theSeconds = (jsdate.getHours() * 3600) + (jsdate.getMinutes() * 60) + jsdate.getSeconds() + off; 
   var beat = Math.floor(theSeconds/86.4); 
   if (beat > 1000) beat -= 1000; 
   if (beat < 0) beat += 1000; 
   if ((String(beat)).length == 1) beat = "00"+beat; 
   if ((String(beat)).length == 2) beat = "0"+beat; 
   return beat; 
  }, 
  g: function(){return jsdate.getHours() % 12 || 12}, 
  G: function(){return jsdate.getHours()}, 
  h: function(){return pad(f.g(), 2)}, 
  H: function(){return pad(jsdate.getHours(), 2)}, 
  i: function(){return pad(jsdate.getMinutes(), 2)}, 
  s: function(){return pad(jsdate.getSeconds(), 2)}, 
  //u not supported yet 
   
  // Timezone 
  //e not supported yet 
  //I not supported yet 
  O: function(){ 
   var t = pad(Math.abs(jsdate.getTimezoneOffset()/60*100), 4); 
   if (jsdate.getTimezoneOffset() > 0) t = "-" + t; else t = "+" + t; 
   return t; 
  }, 
  P: function(){var O = f.O();return (O.substr(0, 3) + ":" + O.substr(3, 2))}, 
  //T not supported yet 
  //Z not supported yet 
   
  // Full Date/Time 
  c: function(){return f.Y() + "-" + f.m() + "-" + f.d() + "T" + f.h() + ":" + f.i() + ":" + f.s() + f.P()}, 
  //r not supported yet 
  U: function(){return Math.round(jsdate.getTime()/1000)} 
 }; 
   
 return format.replace(/[\]?([a-zA-Z])/g, function(t, s){ 
  if( t!=s ){ 
   // escaped 
   ret = s; 
  } else if( f[s] ){ 
   // a date function exists 
   ret = f[s](); 
  } else{ 
   // nothing special 
   ret = s; 
  } 
  return ret; 
 }); 
}

参考
JavaScript Date 对象