datetime - Javascript, Time and Date: Getting the current minute, hour, day, week, month, year of a given millisecond time - Sta

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I'm still wrapping my head around this library, but I'm out of time so I'll just skip to the spoiler section and ask. With a given, arbitrary millisecond time value (like the kind you'd gave from .getTime()), how do I get the current minute, hour, day, week of the month, month, week of the year, and year of that specific millisecond of time?

Additionally, how do I retrieve the number of days of a given month? Anything I should know about regarding leap years and other stuff?

I'm still wrapping my head around this library, but I'm out of time so I'll just skip to the spoiler section and ask. With a given, arbitrary millisecond time value (like the kind you'd gave from .getTime()), how do I get the current minute, hour, day, week of the month, month, week of the year, and year of that specific millisecond of time?

Additionally, how do I retrieve the number of days of a given month? Anything I should know about regarding leap years and other stuff?

• javascript
• datetime

Share Improve this question Follow edited Dec 9, 2010 at 21:12 Hamster asked Dec 9, 2010 at 20:45 HamsterHamster 3,11277 gold badges3030 silver badges3838 bronze badges 1

• It's all explained in the spec. There is a section which describes the date methods, and even the abstract algorithms. – Šime Vidas Commented Dec 9, 2010 at 20:48

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4 Answers 4

Sorted by: Reset to default 161

The variable names should be descriptive:

var date = new Date;
date.setTime(result_from_Date_getTime);

var seconds = date.getSeconds();
var minutes = date.getMinutes();
var hour = date.getHours();

var year = date.getFullYear();
var month = date.getMonth(); // beware: January = 0; February = 1, etc.
var day = date.getDate();

var dayOfWeek = date.getDay(); // Sunday = 0, Monday = 1, etc.
var milliSeconds = date.getMilliseconds();

The days of a given month do not change. In a leap year, February has 29 days. Inspired by http://www.javascriptkata.com/2007/05/24/how-to-know-if-its-a-leap-year/ (thanks Peter Bailey!)

Continued from the previous code:

var days_in_months = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];
// for leap years, February has 29 days. Check whether
// February, the 29th exists for the given year
if( (new Date(year, 1, 29)).getDate() == 29 ) days_in_month[1] = 29;

There is no straightforward way to get the week of a year. For the answer on that question, see Is there a way in javascript to create a date object using year & ISO week number?

Here is another method to get date

new Date().getDate()          // Get the day as a number (1-31)
new Date().getDay()           // Get the weekday as a number (0-6)
new Date().getFullYear()      // Get the four digit year (yyyy)
new Date().getHours()         // Get the hour (0-23)
new Date().getMilliseconds()  // Get the milliseconds (0-999)
new Date().getMinutes()       // Get the minutes (0-59)
new Date().getMonth()         // Get the month (0-11)
new Date().getSeconds()       // Get the seconds (0-59)
new Date().getTime()          // Get the time (milliseconds since January 1, 1970)

Regarding number of days in month just use static switch command and check if (year % 4 == 0) in which case February will have 29 days.

Minute, hour, day etc:

var someMillisecondValue = 511111222127;
var date = new Date(someMillisecondValue);
var minute = date.getMinutes();
var hour = date.getHours();
var day = date.getDate();
var month = date.getMonth();
var year = date.getFullYear();
alert([minute, hour, day, month, year].join("\n"));

Additionally, how do I retrieve the number of days of a given month?

Aside from calculating it yourself (and consequently having to get leap years right), you can use a Date calculation to do it:

var y= 2010, m= 11;            // December 2010 - trap: months are 0-based in JS

var next= Date.UTC(y, m+1);    // timestamp of beginning of following month
var end= new Date(next-1);     // date for last second of this month
var lastday= end.getUTCDate(); // 31

In general for timestamp/date calculations I'd recommend using the UTC-based methods of Date, like getUTCSeconds instead of getSeconds(), and Date.UTC to get a timestamp from a UTC date, rather than new Date(y, m), so you don't have to worry about the possibility of weird time discontinuities where timezone rules change.

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