Constants for General Date Functions

For example, the constant Zend_Date::HOUR can be used in the ways shown below. When working with days of the week, calendar dates, hours, minutes, seconds, and any other date parts that are expressed differently when in different parts of the world, the object's timezone will automatically be used to compute the correct value, even though the internal timestamp is the same for the same moment in time, regardless of the user's physical location in the world. Regardless of the units involved, output must be expressed either as GMT or UTC or localized to a locale. The example output below reflects localization to Europe/GMT+1 hour (e.g. Germany, Austria, France).

Each part of a date or time has a unique constant in Zend_Date. All constants supported by Zend_Date are listed below.

Especially note Zend_Date::DATES, since this format specifier has a unique property within Zend_Date as an input format specifier. When used as an input format for $part, this constant provides the most flexible acceptance of a variety of similar date formats. Heuristics are used to automatically extract dates from an input string and then "fix" simple errors in dates (if any), such as swapping of years, months, and days, when possible.

If you need a date format not shown above, then use a self-defined format composed from the ISO format token specifiers below. The following examples illustrate the usage of constants from the table below to create self-defined ISO formats. The format length is unlimited. Also, multiple usage of format constants is allowed.

The accepted format specifiers can be changed from ISO Format to PHP's date format if you are more comfortable with it. However, not all formats defined in the ISO norm are supported with PHP's date format specifiers. Use the Zend_Date::setOptions(array('format_type' => 'php')) method to switch Zend_Date methods from supporting ISO format specifiers to PHP date() type specifiers (see Self-Defined OUTPUT Formats Using PHP's date() Format Specifiers below).

Note: Note that the default ISO format differs from PHP's format which can be irritating if you have not used in previous. Especially the format specifiers for Year and Minute are often not used in the intended way.
For year there are two specifiers available which are often mistaken. The Y specifier for the ISO year and the y specifier for the real year. The difference is small but significant. Y calculates the ISO year, which is often used for calendar formats. See for example the 31. December 2007. The real year is 2007, but it is the first day of the first week in the week 1 of the year 2008. So, if you are using 'dd.MM.yyyy' you will get '31.December.2007' but if you use 'dd.MM.YYYY' you will get '31.December.2008'. As you see this is no bug but a expected behaviour depending on the used specifiers.
For minute the difference is not so big. ISO uses the specifier m for the minute, unlike PHP which uses i. So if you are getting no minute in your format check if you have used the right specifier.

If you are more comfortable with PHP's date format specifier than with ISO format specifiers, then you can use the Zend_Date::setOptions(array('format_type' => 'php')) method to switch Zend_Date methods from supporting ISO format specifiers to PHP date() type specifiers. Afterwards, all format parameters must be given with » PHP's date() format specifiers. The PHP date format lacks some of the formats supported by the ISO Format, and vice-versa. If you are not already comfortable with it, then use the standard ISO format instead. Also, if you have legacy code using PHP's date format, then either manually convert it to the ISO format using Zend_Locale_Format::convertPhpToIsoFormat(), or use setOptions(). The following examples illustrate the usage of constants from the table below to create self-defined formats.

The following table shows the list of PHP date format specifiers with their equivalent Zend_Date constants and CLDR and ISO equivalent format specifiers. In most cases, when the CLDR and ISO format does not have an equivalent format specifier, the PHP format specifier is not altered by Zend_Locale_Format::convertPhpToIsoFormat(), and the Zend_Date methods then recognize these "peculiar" PHP format specifiers, even when in the default "ISO" format mode.