Date Notes

date = new Date() // creates a date set to the current date and time

Date formats

date = new Date(yy,mm,dd)
date = new Date(yy,mm,dd,hh,mm,ss)
date = new Date("Month dd, yyyy hh:mm:ss")
date = new Date(day, dd mm yyyy hh:mm:ss)
date = new Date("Month dd, yyyy")
date = new Date(milliseconds)

Time values	Day numbers	Month numbers
1 Second = 1000 milliseconds 1 Minute = 60 * 1000 1 Hour = 60 * 60 * 1000 1 Day = 24 * 60 * 60 * 1000 1 Week = 7 * 24 * 60 * 60 * 1000	0 = Sunday 1 = Monday 2 = Tuesday 3 = Wednesday 4 = Thursday 5 = Friday 6 = Saturday	0 = January 1 = February 2 = March 3 = April 4 = May 5 = June 6 = July 7 = August 8 = September 9 = October 10 = November 11 = December

Convert milliseconds into a date

date = new Date(ms) // ms = number of milliseconds since 1 January 1970 00:00:00

Convert a date into milliseconds

milliseconds = date.getTime()
milliseconds = date.parse()
milliseconds = date.UTC(yy,mm,dd,hh,mm,ss)

Adding

today = new Date().getTime()
futureDate = new Date(today + (1000 * 10) add 10 seconds
futureDate = new Date(today + (1000 * 60 * 10) add 10 minites
futureDate = new Date(today + (1000 * 60 * 60 * 10) add 10 hours
futureDate = new Date(today + (1000 * 60 * 60 * 24 * 10) add 10 days
futureDate = new Date(today + (1000 * 60 * 60 * 24 * 7 * 10) add 10 weeks
futureDate = new Date(today + (1000 * 60 * 60 * 24 * 7 * 52 * 10) add 10 years

Calculating between 2 dates

startDate = new Date(2004,02,23,12,12,12)
endDate = new Date(2004,02,01,00,00,00)
period = startDate.getTime() - endDate.getTime()

The result can be express in any one of the following ways

weeks = period / (1000 * 60 * 60 * 24 * 7) will give you 3.215496031746032 number of weeks
days = period / (1000 * 60 * 60 * 24) will give you 22.508472222222224 number of days
hours = period / (1000 * 60 * 60) will give you 540.2033333333334 number of hours
minites = period / (1000 * 60) will give you 32412.2 number of minites
seconds = period / 1000 will give you 1944732 number of seconds

or to get a collective account of weeks, days, hours, minites, and seconds the following

weeks=Math.floor(period/(60*60*1000*24*7))
days=Math.floor(period%(60*60*1000*24*7)/(1000*60*60*24))+1
hours=Math.floor( (period%(60*60*1000*24*7)%(1000*60*60*24))/(1000*60*60))
mins=Math.floor( ( (period%(60*60*1000*24*7) ) %(1000*60*60*24) ) %(1000*60*60)/(1000*60) )
secs=Math.floor( ( ( (period%(60*60*1000*24*7) ) %(1000*60*60*24) ) %(1000*60*60) )%(1000*60)/1000 )

gives you
weeks = 3, days = 2, hours = 12, minites = 12, seconds = 12

Date Object Methods

Method	Description
Retrieving Date Object Values
dateObj.getTime()	GMT milliseconds (+ or -) since zero hours GMT, January 1, 1970
dateObj.getFullYear()	Local year, Cross browser
dateObj.getMonth()	Local month (January = 0)
dateObj.getDate()	Local calendar date number
dateObj.getDay()	Local day of the week (Sunday = 0)
dateObj.getHours()	Local hour of the day (0-23)
dateObj.getMinutes()	Local minutes of the hour (0-59)
dateObj.getSeconds()	Local seconds of the minute (0-59)
Setting Date Object Values
dateObj.setTime()	GMT milliseconds (+ or -) since zero hours GMT, January 1, 1970
dateObj.setYear()	Local year
dateObj.setMonth()	Local month (January = 0)
dateObj.setDate()	Local calendar date number
dateObj.setHours()	Local hour of the day (0-23)
dateObj.setMinutes()	Local minutes of the hour (0-59)
dateObj.setSeconds()	Local seconds of the minute (0-59)
Retrieving Client Time Zone Offset from GMT
dateObj.getTimezoneOffset()	Minutes (+ to west; - to east) offset from GMT
Converting Date Object to Strings
dateObj.toGMTString()	Value as plain language GMT
dateObj.toLocaleString()	Value as plain language local time/date (precise format is platform dependent)
dateObj.toString()	Value as local string (precise format is platform dependent)
Converting GMT Date Values to GMT Milliseconds
Date.parse("IETFDateString")	Converts to GMT ms.
Date.UTC(yy,mm,dd,hh,mm,ss)	Converts to GMT ms.

Note, NS and Moz

With dates prior to 2000, if you use the getYear() method for a date object that holds a 1900 date, the returned value should be the last two digits.

NS and Moz treat the year 2001 as 101.

Use the following to correct

if(year < 1000){
year += 1900
}

Leap Year

A year is a leap year if it is evenly divisible by 4 but not if it's evenly divisible by 100 unless it's also evenly divisible by 400.

isLeap= (((year % 4 == 0) && (year % 100 != 0)) || (year % 400 == 0)) ? 1 : 0

British Summer Time

Summer time is now in force from the last Sunday in March until the last Sunday in October