user_guide_src/source/helpers/date_helper.rst

###########
Date Helper
###########

The Date Helper file contains functions that help you work with dates.

.. contents:: Page Contents

Loading this Helper
===================

This helper is loaded using the following code

::

	$this->load->helper('date');

The following functions are available:

now()
=====

Returns the current time as a Unix timestamp, referenced either to your
server's local time or GMT, based on the "time reference" setting in
your config file. If you do not intend to set your master time reference
to GMT (which you'll typically do if you run a site that lets each user
set their own timezone settings) there is no benefit to using this
function over PHP's time() function.

.. php:method:: now()

mdate()
=======

This function is identical to PHPs `date() <http://www.php.net/date>`_
function, except that it lets you use MySQL style date codes, where each
code letter is preceded with a percent sign: %Y %m %d etc.

The benefit of doing dates this way is that you don't have to worry
about escaping any characters that are not date codes, as you would
normally have to do with the date() function. Example

.. php:method:: mdate($datestr = '', $time = '')

	:param string 	$datestr: Date String
	:param integer 	$time: time
	:returns: integer


::

	$datestring = "Year: %Y Month: %m Day: %d - %h:%i %a";
	$time = time();
	echo mdate($datestring, $time);

If a timestamp is not included in the second parameter the current time
will be used.

standard_date()
===============

Lets you generate a date string in one of several standardized formats.
Example

.. php:method:: standard_date($fmt = 'DATE_RFC822', $time = '')

	:param string 	$fmt: the chosen format
	:param string 	$time: Unix timestamp
	:returns: string

::

	$format = 'DATE_RFC822';
	$time = time();
	echo standard_date($format, $time);

The first parameter must contain the format, the second parameter must
contain the date as a Unix timestamp.

Supported formats:

+----------------+------------------------+-----------------------------------+
| Constant       | Description            | Example                           |
+================+========================+===================================+
| DATE_ATOM      | Atom                   | 2005-08-15T16:13:03+0000          |
+----------------+------------------------+-----------------------------------+
| DATE_COOKIE    | HTTP Cookies           | Sun, 14 Aug 2005 16:13:03 UTC     |
+----------------+------------------------+-----------------------------------+
| DATE_ISO8601   | ISO-8601               | 2005-08-14T16:13:03+00:00         |
+----------------+------------------------+-----------------------------------+
| DATE_RFC822    | RFC 822                | Sun, 14 Aug 05 16:13:03 UTC       |
+----------------+------------------------+-----------------------------------+
| DATE_RFC850    | RFC 850                | Sunday, 14-Aug-05 16:13:03 UTC    |
+----------------+------------------------+-----------------------------------+
| DATE_RFC1036   | RFC 1036               | Sunday, 14-Aug-05 16:13:03 UTC    |
+----------------+------------------------+-----------------------------------+
| DATE_RFC1123   | RFC 1123               | Sun, 14 Aug 2005 16:13:03 UTC     |
+----------------+------------------------+-----------------------------------+
| DATE_RFC2822   | RFC 2822               | Sun, 14 Aug 2005 16:13:03 +0000   |
+----------------+------------------------+-----------------------------------+
| DATE_RSS       | RSS                    | Sun, 14 Aug 2005 16:13:03 UTC     |
+----------------+------------------------+-----------------------------------+
| DATE_W3C       | W3C                    | 2005-08-14T16:13:03+0000          |
+----------------+------------------------+-----------------------------------+


local_to_gmt()
==============

Takes a Unix timestamp as input and returns it as GMT. 

.. php:method:: local_to_gmt($time = '')

	:param integer 	$time: Unix timestamp
	:returns: string

Example:

::

	$now = time();
	$gmt = local_to_gmt($now);

gmt_to_local()
==============

Takes a Unix timestamp (referenced to GMT) as input, and converts it to
a localized timestamp based on the timezone and Daylight Saving time
submitted.

.. php:method:: gmt_to_local($time = '', $timezone = 'UTC', $dst = FALSE)

	:param integer 	$time: Unix timestamp
	:param string 	$timezone: timezone
	:param boolean 	$dst: whether DST is active
	:returns: integer

Example

::

	$timestamp = '1140153693';
	$timezone  = 'UM8';
	$daylight_saving = TRUE;
	echo gmt_to_local($timestamp, $timezone, $daylight_saving);


.. note:: For a list of timezones see the reference at the bottom of this page.


mysql_to_unix()
===============

Takes a MySQL Timestamp as input and returns it as Unix. 

.. php:method:: mysql_to_unix($time = '')

	:param integer 	$time: Unix timestamp
	:returns: integer

Example

::

	$mysql = '20061124092345';
	$unix = mysql_to_unix($mysql);

unix_to_human()
===============

Takes a Unix timestamp as input and returns it in a human readable
format with this prototype

.. php:method:: unix_to_human($time = '', $seconds = FALSE, $fmt = 'us')

	:param integer 	$time: Unix timestamp
	:param boolean 	$seconds: whether to show seconds
	:param string 	$fmt: format: us or euro
	:returns: integer

Example

::

	YYYY-MM-DD HH:MM:SS AM/PM

This can be useful if you need to display a date in a form field for
submission.

The time can be formatted with or without seconds, and it can be set to
European or US format. If only the timestamp is submitted it will return
the time without seconds formatted for the U.S. Examples

::

	$now = time();
	echo unix_to_human($now); // U.S. time, no seconds
	echo unix_to_human($now, TRUE, 'us'); // U.S. time with seconds
	echo unix_to_human($now, TRUE, 'eu'); // Euro time with seconds

human_to_unix()
===============

The opposite of the above function. Takes a "human" time as input and
returns it as Unix. This function is useful if you accept "human"
formatted dates submitted via a form. Returns FALSE (boolean) if the
date string passed to it is not formatted as indicated above. 

.. php:method:: human_to_unix($datestr = '')

	:param integer 	$datestr: Date String
	:returns: integer

Example:

::

	$now = time();
	$human = unix_to_human($now);
	$unix = human_to_unix($human);

nice_date()
===========

This function can take a number poorly-formed date formats and convert
them into something useful. It also accepts well-formed dates.

The function will return a Unix timestamp by default. You can,
optionally, pass a format string (the same type as the PHP date function
accepts) as the second parameter. 

.. php:method:: nice_date($bad_date = '', $format = FALSE) 

	:param integer 	$bad_date: The terribly formatted date-like string
	:param string 	$format: Date format to return (same as php date function)
	:returns: string

Example

::

	$bad_time = 199605  // Should Produce: 1996-05-01
	$better_time = nice_date($bad_time,'Y-m-d');
	$bad_time = 9-11-2001 // Should Produce: 2001-09-11
	$better_time = nice_date($human,'Y-m-d');

timespan()
==========

Formats a unix timestamp so that is appears similar to this

::

	1 Year, 10 Months, 2 Weeks, 5 Days, 10 Hours, 16 Minutes

The first parameter must contain a Unix timestamp. The second parameter
must contain a timestamp that is greater that the first timestamp. If
the second parameter empty, the current time will be used. The third 
parameter is optional and limits the number of time units to display. 
The most common purpose for this function is to show how much time has 
elapsed from some point in time in the past to now. 

.. php:method:: timespan($seconds = 1, $time = '', $units = '')

	:param integer 	$seconds: a number of seconds
	:param string 	$time: Unix timestamp
	:param integer 	$units: a number of time units to display
	:returns: string

Example

::

	$post_date = '1079621429';
	$now = time();
	$units = 2;
	echo timespan($post_date, $now, $units);

.. note:: The text generated by this function is found in the following language
	file: language/<your_lang>/date_lang.php

days_in_month()
===============

Returns the number of days in a given month/year. Takes leap years into
account. 

.. php:method:: days_in_month($month = 0, $year = '')

	:param integer 	$month: a numeric month
	:param integer 	$year: a numeric year
	:returns: integer

Example

::

	echo days_in_month(06, 2005);

If the second parameter is empty, the current year will be used.

timezones()
===========

Takes a timezone reference (for a list of valid timezones, see the
"Timezone Reference" below) and returns the number of hours offset from
UTC.

.. php:method:: timezones($tz = '')

	:param string 	$tz: a numeric timezone
	:returns: string

Example

::

	echo timezones('UM5');


This function is useful when used with `timezone_menu()`.

timezone_menu()
===============

Generates a pull-down menu of timezones, like this one:


.. raw:: html

	<form action="#">
		<select name="timezones">
			<option value='UM12'>(UTC -12:00) Baker/Howland Island</option>
			<option value='UM11'>(UTC -11:00) Samoa Time Zone, Niue</option>
			<option value='UM10'>(UTC -10:00) Hawaii-Aleutian Standard Time, Cook Islands, Tahiti</option>
			<option value='UM95'>(UTC -9:30) Marquesas Islands</option>
			<option value='UM9'>(UTC -9:00) Alaska Standard Time, Gambier Islands</option>
			<option value='UM8'>(UTC -8:00) Pacific Standard Time, Clipperton Island</option>
			<option value='UM7'>(UTC -7:00) Mountain Standard Time</option>
			<option value='UM6'>(UTC -6:00) Central Standard Time</option>
			<option value='UM5'>(UTC -5:00) Eastern Standard Time, Western Caribbean Standard Time</option>
			<option value='UM45'>(UTC -4:30) Venezuelan Standard Time</option>
			<option value='UM4'>(UTC -4:00) Atlantic Standard Time, Eastern Caribbean Standard Time</option>
			<option value='UM35'>(UTC -3:30) Newfoundland Standard Time</option>
			<option value='UM3'>(UTC -3:00) Argentina, Brazil, French Guiana, Uruguay</option>
			<option value='UM2'>(UTC -2:00) South Georgia/South Sandwich Islands</option>
			<option value='UM1'>(UTC -1:00) Azores, Cape Verde Islands</option>
			<option value='UTC' selected='selected'>(UTC) Greenwich Mean Time, Western European Time</option>
			<option value='UP1'>(UTC +1:00) Central European Time, West Africa Time</option>
			<option value='UP2'>(UTC +2:00) Central Africa Time, Eastern European Time, Kaliningrad Time</option>
			<option value='UP3'>(UTC +3:00) Moscow Time, East Africa Time</option>
			<option value='UP35'>(UTC +3:30) Iran Standard Time</option>
			<option value='UP4'>(UTC +4:00) Azerbaijan Standard Time, Samara Time</option>
			<option value='UP45'>(UTC +4:30) Afghanistan</option>
			<option value='UP5'>(UTC +5:00) Pakistan Standard Time, Yekaterinburg Time</option>
			<option value='UP55'>(UTC +5:30) Indian Standard Time, Sri Lanka Time</option>
			<option value='UP575'>(UTC +5:45) Nepal Time</option>
			<option value='UP6'>(UTC +6:00) Bangladesh Standard Time, Bhutan Time, Omsk Time</option>
			<option value='UP65'>(UTC +6:30) Cocos Islands, Myanmar</option>
			<option value='UP7'>(UTC +7:00) Krasnoyarsk Time, Cambodia, Laos, Thailand, Vietnam</option>
			<option value='UP8'>(UTC +8:00) Australian Western Standard Time, Beijing Time, Irkutsk Time</option>
			<option value='UP875'>(UTC +8:45) Australian Central Western Standard Time</option>
			<option value='UP9'>(UTC +9:00) Japan Standard Time, Korea Standard Time, Yakutsk Time</option>
			<option value='UP95'>(UTC +9:30) Australian Central Standard Time</option>
			<option value='UP10'>(UTC +10:00) Australian Eastern Standard Time, Vladivostok Time</option>
			<option value='UP105'>(UTC +10:30) Lord Howe Island</option>
			<option value='UP11'>(UTC +11:00) Magadan Time, Solomon Islands, Vanuatu</option>
			<option value='UP115'>(UTC +11:30) Norfolk Island</option>
			<option value='UP12'>(UTC +12:00) Fiji, Gilbert Islands, Kamchatka Time, New Zealand Standard Time</option>
			<option value='UP1275'>(UTC +12:45) Chatham Islands Standard Time</option>
			<option value='UP13'>(UTC +13:00) Phoenix Islands Time, Tonga</option>
			<option value='UP14'>(UTC +14:00) Line Islands</option>
		</select>
	</form>


This menu is useful if you run a membership site in which your users are
allowed to set their local timezone value.

The first parameter lets you set the "selected" state of the menu. For
example, to set Pacific time as the default you will do this

.. php:method:: timezone_menu($default = 'UTC', $class = "", $name = 'timezones')

	:param string 	$default: timezone
	:param string	$class: classname
	:param string	$name: menu name
	:returns: string

Example: 

::

	echo timezone_menu('UM8');

Please see the timezone reference below to see the values of this menu.

The second parameter lets you set a CSS class name for the menu.

.. note:: The text contained in the menu is found in the following
	language file: `language/<your_lang>/date_lang.php`


Timezone Reference
==================

The following table indicates each timezone and its location.

Note some of the location lists have been abridged for clarity and formatting.

+------------+----------------------------------------------------------------+
| Time Zone  | Location                                                       |
+============+================================================================+
| UM12       | (UTC - 12:00) Baker/Howland Island	                          |
+------------+----------------------------------------------------------------+
| UM11       | (UTC - 11:00) Samoa Time Zone, Niue						      |
+------------+----------------------------------------------------------------+
| UM10       | (UTC - 10:00) Hawaii-Aleutian Standard Time, Cook Islands	  |
+------------+----------------------------------------------------------------+
| UM95       | (UTC - 09:30) Marquesas Islands							      |
+------------+----------------------------------------------------------------+
| UM9        | (UTC - 09:00) Alaska Standard Time, Gambier Islands		      |
+------------+----------------------------------------------------------------+
| UM8        | (UTC - 08:00) Pacific Standard Time, Clipperton Island	      |
+------------+----------------------------------------------------------------+
| UM7        | (UTC - 11:00) Mountain Standard Time						      |
+------------+----------------------------------------------------------------+
| UM6        | (UTC - 06:00) Central Standard Time						      |
+------------+----------------------------------------------------------------+
| UM5        | (UTC - 05:00) Eastern Standard Time, Western Caribbean		  |
+------------+----------------------------------------------------------------+
| UM45       | (UTC - 04:30) Venezuelan Standard Time					      |
+------------+----------------------------------------------------------------+
| UM4        | (UTC - 04:00) Atlantic Standard Time, Eastern Caribbean		  |
+------------+----------------------------------------------------------------+
| UM35       | (UTC - 03:30) Newfoundland Standard Time					      |
+------------+----------------------------------------------------------------+
| UM3        | (UTC - 03:00) Argentina, Brazil, French Guiana, Uruguay	      |
+------------+----------------------------------------------------------------+
| UM2        | (UTC - 02:00) South Georgia/South Sandwich Islands		      |
+------------+----------------------------------------------------------------+
| UM1        | (UTC -1:00) Azores, Cape Verde Islands						  |
+------------+----------------------------------------------------------------+
| UTC        | (UTC) Greenwich Mean Time, Western European Time				  |
+------------+----------------------------------------------------------------+
| UP1        | (UTC +1:00) Central European Time, West Africa Time			  |
+------------+----------------------------------------------------------------+
| UP2        | (UTC +2:00) Central Africa Time, Eastern European Time		  |
+------------+----------------------------------------------------------------+
| UP3        | (UTC +3:00) Moscow Time, East Africa Time			  		  |
+------------+----------------------------------------------------------------+
| UP35       | (UTC +3:30) Iran Standard Time								  |
+------------+----------------------------------------------------------------+
| UP4        | (UTC +4:00) Azerbaijan Standard Time, Samara Time			  |
+------------+----------------------------------------------------------------+
| UP45       | (UTC +4:30) Afghanistan										  |
+------------+----------------------------------------------------------------+
| UP5        | (UTC +5:00) Pakistan Standard Time, Yekaterinburg Time		  |
+------------+----------------------------------------------------------------+
| UP55       | (UTC +5:30) Indian Standard Time, Sri Lanka Time				  |
+------------+----------------------------------------------------------------+
| UP575      | (UTC +5:45) Nepal Time										  |
+------------+----------------------------------------------------------------+
| UP6        | (UTC +6:00) Bangladesh Standard Time, Bhutan Time, Omsk Time   |
+------------+----------------------------------------------------------------+
| UP65       | (UTC +6:30) Cocos Islands, Myanmar							  |
+------------+----------------------------------------------------------------+
| UP7        | (UTC +7:00) Krasnoyarsk Time, Cambodia, Laos, Thailand, Vietnam|
+------------+----------------------------------------------------------------+
| UP8        | (UTC +8:00) Australian Western Standard Time, Beijing Time	  |
+------------+----------------------------------------------------------------+
| UP875      | (UTC +8:45) Australian Central Western Standard Time		      |
+------------+----------------------------------------------------------------+
| UP9        | (UTC +9:00) Japan Standard Time, Korea Standard Time, Yakutsk  |
+------------+----------------------------------------------------------------+
| UP95       | (UTC +9:30) Australian Central Standard Time					  |
+------------+----------------------------------------------------------------+
| UP10       | (UTC +10:00) Australian Eastern Standard Time, Vladivostok Time|
+------------+----------------------------------------------------------------+
| UP105      | (UTC +10:30) Lord Howe Island								  |
+------------+----------------------------------------------------------------+
| UP11       | (UTC +11:00) Magadan Time, Solomon Islands, Vanuatu            |
+------------+----------------------------------------------------------------+
| UP115      | (UTC +11:30) Norfolk Island									  |
+------------+----------------------------------------------------------------+
| UP12       | (UTC +12:00) Fiji, Gilbert Islands, Kamchatka, New Zealand     |
+------------+----------------------------------------------------------------+
| UP1275     | (UTC +12:45) Chatham Islands Standard Time					  |
+------------+----------------------------------------------------------------+
| UP13       | (UTC +13:00) Phoenix Islands Time, Tonga						  |
+------------+----------------------------------------------------------------+
| UP14       | (UTC +14:00) Line Islands									  |
+------------+----------------------------------------------------------------+