Zend_Date API OverviewWhile the Zend_Date API remains simplistic and unitary, its design remains flexible and powerful through the rich permutations of operations and operands. Zend_Date OptionsSelecting the Date Format TypeSeveral methods use date format strings, in a way similar to PHP's date(). If you are more comfortable with PHP's date format specifier than with ISO format specifiers, then you can use Zend_Date::setOptions(array('format_type' => 'php')). Afterward, use PHP's date format specifiers for all functions which accept a $format parameter. Use Zend_Date::setOptions(array('format_type' => 'iso')) to switch back to the default mode of supporting only ISO date format tokens. For a list of supported format codes, see Self-Defined OUTPUT Formats Using PHP's date() Format Specifiers DST and Date MathWhen dates are manipulated, sometimes they cross over a DST change, normally resulting in the date losing or gaining an hour. For exmaple, when adding months to a date before a DST change, if the resulting date is after the DST change, then the resulting date will appear to lose or gain an hour, resulting in the time value of the date changing. For boundary dates, such as midnight of the first or last day of a month, adding enough months to cross a date boundary results in the date losing an hour and becoming the last hour of the preceding month, giving the appearance of an "off by 1" error. To avoid this situation, the DST change ignored by using the fix_dst option. When crossing the Summer or Winter DST boundary, normally an hour is substracted or added depending on the date. For example, date math crossing the Spring DST leads to a date having a day value one less than expected, if the time part of the date was originally 00:00:00. Since Zend_Date is based on timestamps, and not calendar dates with a time component, the timestamp loses an hour, resulting in the date having a calendar day value one less than expected. To prevent such problems use the option fix_dst, which defaults to TRUE, causing DST to have no effect on date "math" ( addMonth(), subMonth()). Use Zend_Date::setOptions(array('fix_dst' => false)) to enable the subtraction or addition of the DST adjustment when performing date "math". If your actual timezone within the instance of Zend_Date is set to UTC or GMT the option 'fix_dst' will not be used because these two timezones do not work with DST. When you change the timezone for this instance again to a timezone which is not UTC or GMT the previous set 'fix_dst' option will be used again for date "math". Month CalculationsWhen adding or substracting months from an existing date, the resulting value for the day of the month might be unexpected, if the original date fell on a day close to the end of the month. For example, when adding one month to January 31st, people familiar with SQL will expect February 28th as the result. On the other side, people familiar with Excel and OpenOffice will expect March 3rd as the result. The problem only occurs, if the resulting month does not have the day, which is set in the original date. For Zend Framework developers, the desired behavior is selectable using the extend_month option to choose either the SQL behaviour, if set to FALSE, or the spreadsheet behaviour when set to TRUE. The default behaviour for extend_month is FALSE, providing behavior compatible to SQL. By default, Zend_Date computes month calculations by truncating dates to the end of the month (if necessary), without wrapping into the next month when the original date designates a day of the month exceeding the number of days in the resulting month. Use Zend_Date::setOptions(array('extend_month' => true)) to make month calculations work like popular spreadsheet programs. Speed up Date Localization and Normalization with Zend_CacheYou can speed up Zend_Date by using an Zend_Cache adapter. This speeds up all methods of Zend_Date when you are using localized data. For example all methods which accept Zend_Date::DATE and Zend_Date::TIME constants would benefit from this. To set an Zend_Cache adapter to Zend_Date just use Zend_Date::setOptions(array('cache' => $adapter)). Receiving Syncronised Timestamps with Zend_TimeSyncNormally the clocks from servers and computers differ from each other. Zend_Date is able to handle such problems with the help of Zend_TimeSync. You can set a timeserver with Zend_Date::setOptions(array('timesync' => $timeserver)) which will set the offset between the own actual timestamp and the real actual timestamp for all instances of Zend_Date. Using this option does not change the timestamp of existing instances. So best usage is to set it within the bootstrap file. Working with Date ValuesOnce input has been normalized via the creation of a Zend_Date object, it will have an associated timezone, but an internal representation using standard » UNIX timestamps. In order for a date to be rendered in a localized manner, a timezone must be known first. The default timezone is always GMT or UTC. To examine an object's timezone use getTimeZone(). To change an object's timezone, use setTimeZone(). All manipulations of these objects are assumed to be relative to this timezone. Beware of mixing and matching operations with date parts between date objects for different timezones, which generally produce undesireable results, unless the manipulations are only related to the timestamp. Operating on Zend_Date objects having different timezones generally works, except as just noted, since dates are normalized to UNIX timestamps on instantiation of Zend_Date. Most methods expect a constant selecting the desired $part of a date, such as Zend_Date::HOUR. These constants are valid for all of the functions below. A list of all available constants is provided in list of all constants. If no $part is specified, then Zend_Date::TIMESTAMP is assumed. Alternatively, a user-specified format may be used for $part, using the same underlying mechanism and format codes as Zend_Locale_Format::getDate(). If a date object is constructed using an obviously invalid date (e.g. a month number greater than 12), then Zend_Date will throw an exception, unless no specific date format has been selected -i.e. $part is either NULL or Zend_Date::DATES (a "loose" format). Example #1 User-Specified Input Date Format
If the optional $locale parameter is provided, then the $locale disambiguates the $date operand by replacing month and weekday names for string $date operands, and even parsing date strings expressed according to the conventions of that locale (see Zend_Locale_Format::getDate()). The automatic normalization of localized $date operands of a string type occurs when $part is one of the Zend_Date::DATE* or Zend_Date::TIME* constants. The locale identifies which language should be used to parse month names and weekday names, if the $date is a string containing a date. If there is no $date input parameter, then the $locale parameter specifies the locale to use for localizing output (e.g. the date format for a string representation). Note that the $date input parameter might actually have a type name instead (e.g. $hour for addHour()), although that does not prevent the use of Zend_Date objects as arguments for that parameter. If no $locale was specified, then the locale of the current object is used to interpret $date, or select the localized format for output. Since Zend Framework 1.7.0 Zend_Date does also support the usage of an application wide locale. You can simply set a Zend_Locale instance to the registry like shown below. With this notation you can forget about setting the locale manually with each instance when you want to use the same locale multiple times.
Basic Zend_Date Operations Common to Many Date PartsThe methods add(), sub(), compare(), get(), and set() operate generically on dates. In each case, the operation is performed on the date held in the instance object. The $date operand is required for all of these methods, except get(), and may be a Zend_Date instance object, a numeric string, or an integer. These methods assume $date is a timestamp, if it is not an object. However, the $part operand controls which logical part of the two dates are operated on, allowing operations on parts of the object's date, such as year or minute, even when $date contains a long form date string, such as, "December 31, 2007 23:59:59". The result of the operation changes the date in the object, except for compare(), and get(). Example #2 Operating on Parts of Dates
Convenience methods exist for each combination of the basic operations and several common date parts as shown in the tables below. These convenience methods help us lazy programmers avoid having to type out the date part constants when using the general methods above. Conveniently, they are named by combining a prefix (name of a basic operation) with a suffix (type of date part), such as addYear(). In the list below, all combinations of "Date Parts" and "Basic Operations" exist. For example, the operation "add" exists for each of these date parts, including addDay(), addYear(), etc. These convenience methods have the same equivalent functionality as the basic operation methods, but expect string and integer $date operands containing only the values representing the type indicated by the suffix of the convenience method. Thus, the names of these methods (e.g. "Year" or "Minute") identify the units of the $date operand, when $date is a string or integer. List of Date Parts
List of Date OperationsThe basic operations below can be used instead of the convenience operations for specific date parts, if the appropriate constant is used for the $part parameter.
Comparing DatesThe following basic operations do not have corresponding convenience methods for the date parts listed in Zend_Date API Overview.
Getting Dates and Date PartsSeveral methods support retrieving values related to a Zend_Date instance.
Working with Fractions of SecondsSeveral methods support retrieving values related to a Zend_Date instance.
Sunrise / SunsetThree methods provide access to geographically localized information about the Sun, including the time of sunrise and sunset.
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