对此，我写了以下函数，支持ie6+，谷歌，火狐等浏览器：

代码如下:
function getTime(day){
re = /(\d{4})(?:-(\d{1,2})(?:-(\d{1,2}))?)?(?:\s+(\d{1,2}):(\d{1,2}):(\d{1,2}))?/.exec(day);
return new Date(re[1],(re[2]||1)-1,re[3]||1,re[4]||0,re[5]||0,re[6]||0).getTime()/1000;
}

//test
alert(getTime("2013-02-03 10:10:10"));
alert(getTime("2013-02-03"));
alert(getTime("2013-02"));
alert(getTime("2013"));

下面这个将时间戳转换成日期格式的函数，支持自定义的日期格式，效果类似PHP的date函数，同样支持ie6+，谷歌，火狐等浏览器。这个函数是网友实现的，以后有时间我也写一个出来 ^_^

代码如下:
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")) / 8e5 >> 0},

// Week
W: function(){
var a = f.z(), b = 3 + 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;
});
}

//test
alert(date('Y-m-d H:i:s',(new Date).getTime()/1000));
alert(date('Y-m-d',(new Date).getTime()/1000));
alert(date('Y-m-d H:i:s','1355252653'));