Date and time

Objectives

• create and modify JavaScript Date objects
• format dates and times to suit needs
• create Date objects with specific times in the future or past
• use a custom date formatting routine: dateformat.js

Date object

• stores date as milliseconds since 1/1/1970 start of day
• days before then are stored as negative milliseconds
• no accuracy guaranteed for days before 1/1/1970
• constructors
  • Date()
    • uses current date and time
    • returns a string representation of the current date and time if called as a regular function
  • Date(milliseconds)
    • sets new Date object to milliseconds since 1/1/1970 start of day
  • Date(datestring)
    • uses any string handled by Date.parse to set new Date object
  • Date(year, month[, day[, hours[, minutes[, seconds[, milliseconds]]]]])
  • many optional fields: day, hours, minutes, seconds, milliseconds
  • year: 0-99 get 1900 added to them
  • month: 0-11
  • day: 1-31
  • hours: 0-23
  • minutes: 0-59
  • seconds: 0-59
  • milliseconds: 0-999
• static methods:
  • now(): returns the current time in milliseconds
  • parse(datestring): parses a string representation of a date/time and returns the millisecond representation
  • UTC(year, month, day[, hours[, minutes[, seconds[, milliseconds]]]]): returns the millisecond representation of the specified UTC time
• methods:
  • getDate(): 1-31
  • getDay(): 0-6
  • getFullYear(): returns four digit year
  • getHours(): 0-23
  • getMilliseconds(): 0-999
  • getMinutes(): 0-59
  • getMonth(): 0-11
  • getSeconds(): 0-59
  • getTime(): returns millisecond representation of date
  • getTimezoneOffset(): returns difference in minutes between local time and UTC time
  • getYear(): (deprecated) use getFullYear() instead
  • setDate(): 0-31
  • setFullYear(): use four digit year value
  • setHours(): 0-23
  • setMilliseconds(): 0-999
  • setMinutes(): 0-59
  • setMonth(): 0-11
  • setSeconds(): 0-59
  • setTime(): sets date/time using milliseconds
  • setYear(): (deprecated) use setFullYear() instead
  • toUTCString(): returns UTC version of date/time
  • toGMTString(): returns GMT version of date/time (deprecated - use toUTCString() instead)
  • toISOString(): returns ISO-8601 version of date/time
  • toJSON(): uses toISOString() to serialize a Date object
  • toLocaleString(): returns local version of date/time
  • toLocaleDateString(): returns local version of date (not time)
  • toLocaleTimeString(): returns local version of time (not date)
  • toString(): returns local version of date/time
  • toDateString(): returns local version of date (not time)
  • toTimeString(): returns local version of time (not date)
  • valueOf(): returns millisecond representation of date/time
• UTC versions of some of the above methods:
  • getUTCDate()
  • getUTCDay()
  • getUTCFullYear()
  • getUTCHours()
  • getUTCMilliseconds()
  • getUTCMinutes()
  • getUTCMonth()
  • getUTCSeconds()
  • setUTCDate()
  • setUTCFullYear()
  • setUTCHours()
  • setUTCMilliseconds()
  • setUTCMinutes()
  • setUTCMonth()
  • setUTCSeconds()

Examples

• creating Date objects, setting the year
• calculating day of week, month, creating new Date objects with a given date, using Date functions
• looking in to the future
• converting miltary and normal time
• getting ready for Christmas
• creating this month's calendar dynamically
• creating any month's calendar
• adding a format string method to the Date class

Date string formatter example

• The following code can be executed to add an easy date formatting funtion to the built-in Date class.
• The caller passes in a string which is passed right back to the caller, except that certain character sequences are replaced with date information.
• The date information is based on the values in the date object used to call the method.
• {$day} is replaced with the full day name: Sunday, Monday, ...
• {$shortDay} is replaced with the short day name: Sun, Mon, ...
• {$date} is replaced with the day of the month: 1, 2, 3, ...
• {$suffix} is replaced with a date suffix: st, nd, rd, th, th, ...
• {$monthNum} is replaced with the month number: 1, 2, 3, ...
• {$month} is replaced with the full month name: January, February, ...
• {$shortMonth} is replaced with the short month name: Jan, Feb, ...
• {$year} is replaced with the the full four digit year number
• {$shortYear} is replaced with the last two digits of the year

Result of above code run on 2013-05-12