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

Question

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?

Answer 1

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?