Date/Time 函数
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date

(PHP 4, PHP 5)

date — 格式化一个本地时间／日期

说明

string date ( string $format [, int $timestamp ] )

返回将整数 timestamp 按照给定的格式字串而产生的字符串。如果没有给出时间戳则使用本地当前时间。换句话说，timestamp 是可选的，默认值为 time()。

Tip

自 PHP 5.1.1 起有几个有用的常量可用作标准的日期／时间格式来指定 format 参数。

Tip

自 PHP 5.1 起在 $_SERVER['REQUEST_TIME'] 中保存了发起该请求时刻的时间戳。

Note:

有效的时间戳典型范围是格林威治时间 1901 年 12 月 13 日 20:45:54 到 2038 年 1 月 19 日 03:14:07。（此范围符合 32 位有符号整数的最小值和最大值）。不过在 PHP 5.1 之前此范围在某些系统（如 Windows）中限制为从 1970 年 1 月 1 日到 2038 年 1 月 19 日。

Note:

要将字符串表达的时间转换成时间戳，应该使用 strtotime()。此外一些数据库有一些函数将其时间格式转换成时间戳（例如 MySQL 的 » UNIX_TIMESTAMP 函数）。

格式字串可以识别以下 format 参数的字符串
format 字符 说明 返回值例子
日 --- ---
d 月份中的第几天，有前导零的 2 位数字 01 到 31
D 星期中的第几天，文本表示，3 个字母 Mon 到 Sun
j 月份中的第几天，没有前导零 1 到 31
l（“L”的小写字母） 星期几，完整的文本格式 Sunday 到 Saturday
N ISO-8601 格式数字表示的星期中的第几天（PHP 5.1.0 新加） 1（表示星期一）到 7（表示星期天）
S 每月天数后面的英文后缀，2 个字符 st，nd，rd 或者 th。可以和 j 一起用
w 星期中的第几天，数字表示 0（表示星期天）到 6（表示星期六）
z 年份中的第几天 0 到 366
星期 --- ---
W ISO-8601 格式年份中的第几周，每周从星期一开始（PHP 4.1.0 新加的） 例如：42（当年的第 42 周）
月 --- ---
F 月份，完整的文本格式，例如 January 或者 March January 到 December
m 数字表示的月份，有前导零 01 到 12
M 三个字母缩写表示的月份 Jan 到 Dec
n 数字表示的月份，没有前导零 1 到 12
t 给定月份所应有的天数 28 到 31
年 --- ---
L 是否为闰年 如果是闰年为 1，否则为 0
o ISO-8601 格式年份数字。这和 Y 的值相同，只除了如果 ISO 的星期数（W）属于前一年或下一年，则用那一年。（PHP 5.1.0 新加） Examples: 1999 or 2003
Y 4 位数字完整表示的年份 例如：1999 或 2003
y 2 位数字表示的年份 例如：99 或 03
时间 --- ---
a 小写的上午和下午值 am 或 pm
A 大写的上午和下午值 AM 或 PM
B Swatch Internet 标准时 000 到 999
g 小时，12 小时格式，没有前导零 1 到 12
G 小时，24 小时格式，没有前导零 0 到 23
h 小时，12 小时格式，有前导零 01 到 12
H 小时，24 小时格式，有前导零 00 到 23
i 有前导零的分钟数 00 到 59>
s 秒数，有前导零 00 到 59>
时区 --- ---
e 时区标识（PHP 5.1.0 新加） 例如：UTC，GMT，Atlantic/Azores
I 是否为夏令时 如果是夏令时为 1，否则为 0
O 与格林威治时间相差的小时数 例如：+0200
P 与格林威治时间（GMT）的差别，小时和分钟之间有冒号分隔（PHP 5.1.3 新加） 例如：+02:00
T 本机所在的时区 例如：EST，MDT（【译者注】在 Windows 下为完整文本格式，例如“Eastern Standard Time”，中文版会显示“中国标准时间”）。
Z 时差偏移量的秒数。UTC 西边的时区偏移量总是负的，UTC 东边的时区偏移量总是正的。 -43200 到 43200
完整的日期／时间 --- ---
c ISO 8601 格式的日期（PHP 5 新加） 2004-02-12T15:19:21+00:00
r RFC 822 格式的日期 例如：Thu, 21 Dec 2000 16:01:07 +0200
U 从 Unix 纪元（January 1 1970 00:00:00 GMT）开始至今的秒数 参见 time()

格式字串中不能被识别的字符将原样显示。Z 格式在使用 gmdate() 时总是返回 0。

Example #1 date() 例子

<?php
// 设定要用的默认时区。自 PHP 5.1 可用
date_default_timezone_set('UTC');


// 输出类似：Monday
echo date("l");

// 输出类似：Monday 15th of August 2005 03:12:46 PM
echo date('l dS \of F Y h:i:s A');

// 输出：July 1, 2000 is on a Saturday
echo "July 1, 2000 is on a " . date("l", mktime(0, 0, 0, 7, 1, 2000));

/* 在格式参数中使用常量 */
// 输出类似：Mon, 15 Aug 2005 15:12:46 UTC
echo date(DATE_RFC822);

// 输出类似：2000-07-01T00:00:00+00:00
echo date(DATE_ATOM, mktime(0, 0, 0, 7, 1, 2000));
?>

在格式字串中的字符前加上反斜线来转义可以避免它被按照上表解释。如果加上反斜线后的字符本身就是一个特殊序列，那还要转义反斜线。

Example #2 在 date() 中转义字符

<?php
// prints something like: Wednesday the 15th
echo date("l \\t\h\e jS");
?>

可以把 date() 和 mktime() 结合使用来得到未来或过去的日期。

Example #3 date() 和 mktime() 例子

<?php
$tomorrow  = mktime(0, 0, 0, date("m")  , date("d")+1, date("Y"));
$lastmonth = mktime(0, 0, 0, date("m")-1, date("d"),   date("Y"));
$nextyear  = mktime(0, 0, 0, date("m"),   date("d"),   date("Y")+1);
?>

Note:

由于夏令时的缘故，这种方法比简单地在时间戳上加减一天或者一个月的秒数更可靠。

一些使用 date() 格式化日期的例子。注意要转义所有其它的字符，因为目前有特殊含义的字符会产生不需要的结果，而其余字符在 PHP 将来的版本中可能会被用上。当转义时，注意用单引号以避免类似 \n 的字符变成了换行符。

Example #4 date() 格式举例

<?php
// 假定今天是：March 10th, 2001, 5:16:18 pm
$today = date("F j, Y, g:i a");                 // March 10, 2001, 5:16 pm
$today = date("m.d.y");                         // 03.10.01
$today = date("j, n, Y");                       // 10, 3, 2001
$today = date("Ymd");                           // 20010310
$today = date('h-i-s, j-m-y, it is w Day z ');  // 05-16-17, 10-03-01, 1631 1618 6 Fripm01
$today = date('\i\t \i\s \t\h\e jS \d\a\y.');   // It is the 10th day.
$today = date("D M j G:i:s T Y");               // Sat Mar 10 15:16:08 MST 2001
$today = date('H:m:s \m \i\s\ \m\o\n\t\h');     // 17:03:17 m is month
$today = date("H:i:s");                         // 17:16:17
?>

要格式化其它语种的日期，应该用 setlocale() 和 strftime() 函数来代替 date()。

参见 getlastmod()，gmdate()，mktime()，strftime() 和 time()。

参数

format

The format of the outputted date string. See the formatting options below. There are also several predefined date constants that may be used instead, so for example DATE_RSS contains the format string 'D, d M Y H:i:s'.

The following characters are recognized in the format parameter string
format character Description Example returned values
Day --- ---
d Day of the month, 2 digits with leading zeros 01 to 31
D A textual representation of a day, three letters Mon through Sun
j Day of the month without leading zeros 1 to 31
l (lowercase 'L') A full textual representation of the day of the week Sunday through Saturday
N ISO-8601 numeric representation of the day of the week (added in PHP 5.1.0) 1 (for Monday) through 7 (for Sunday)
S English ordinal suffix for the day of the month, 2 characters st, nd, rd or th. Works well with j
w Numeric representation of the day of the week 0 (for Sunday) through 6 (for Saturday)
z The day of the year (starting from 0) 0 through 365
Week --- ---
W ISO-8601 week number of year, weeks starting on Monday (added in PHP 4.1.0) Example: 42 (the 42nd week in the year)
Month --- ---
F A full textual representation of a month, such as January or March January through December
m Numeric representation of a month, with leading zeros 01 through 12
M A short textual representation of a month, three letters Jan through Dec
n Numeric representation of a month, without leading zeros 1 through 12
t Number of days in the given month 28 through 31
Year --- ---
L Whether it's a leap year 1 if it is a leap year, 0 otherwise.
o ISO-8601 year number. This has the same value as Y, except that if the ISO week number (W) belongs to the previous or next year, that year is used instead. (added in PHP 5.1.0) Examples: 1999 or 2003
Y A full numeric representation of a year, 4 digits Examples: 1999 or 2003
y A two digit representation of a year Examples: 99 or 03
Time --- ---
a Lowercase Ante meridiem and Post meridiem am or pm
A Uppercase Ante meridiem and Post meridiem AM or PM
B Swatch Internet time 000 through 999
g 12-hour format of an hour without leading zeros 1 through 12
G 24-hour format of an hour without leading zeros 0 through 23
h 12-hour format of an hour with leading zeros 01 through 12
H 24-hour format of an hour with leading zeros 00 through 23
i Minutes with leading zeros 00 to 59
s Seconds, with leading zeros 00 through 59
u Microseconds (added in PHP 5.2.2) Example: 654321
Timezone --- ---
e Timezone identifier (added in PHP 5.1.0) Examples: UTC, GMT, Atlantic/Azores
I (capital i) Whether or not the date is in daylight saving time 1 if Daylight Saving Time, 0 otherwise.
O Difference to Greenwich time (GMT) in hours Example: +0200
P Difference to Greenwich time (GMT) with colon between hours and minutes (added in PHP 5.1.3) Example: +02:00
T Timezone abbreviation Examples: EST, MDT ...
Z Timezone offset in seconds. The offset for timezones west of UTC is always negative, and for those east of UTC is always positive. -43200 through 50400
Full Date/Time --- ---
c ISO 8601 date (added in PHP 5) 2004-02-12T15:19:21+00:00
r » RFC 2822 formatted date Example: Thu, 21 Dec 2000 16:01:07 +0200
U Seconds since the Unix Epoch (January 1 1970 00:00:00 GMT) See also time()

Unrecognized characters in the format string will be printed as-is. The Z format will always return 0 when using gmdate().

Note:

Since this function only accepts integer timestamps the u format character is only useful when using the date_format() function with user based timestamps created with date_create().

timestamp

可选的 timestamp 参数是一个 integer 的 Unix 时间戳，如未指定，参数值默认为当前本地时间。也就是说，其值默认为 time() 的返回值。

返回值

Returns a formatted date string. If a non-numeric value is used for timestamp, FALSE is returned and an E_WARNING level error is emitted.

错误/异常

在每 次调用日期/时间函数时，如果时区无效则会引发 E_NOTICE 错误，如果使用系统设定值或 TZ 环境变量，则会引发 E_STRICT 或 E_WARNING 消息。参见 date_default_timezone_set()

更新日志

版本 说明
5.1.0 The valid range of a timestamp is typically from Fri, 13 Dec 1901 20:45:54 GMT to Tue, 19 Jan 2038 03:14:07 GMT. (These are the dates that correspond to the minimum and maximum values for a 32-bit signed integer). However, before PHP 5.1.0 this range was limited from 01-01-1970 to 19-01-2038 on some systems (e.g. Windows).
5.1.0

现在发布 E_STRICT 和 E_NOTICE 时区错误。

5.1.1 There are useful constants of standard date/time formats that can be used to specify the format parameter.

范例

Example #5 date() examples

<?php
// set the default timezone to use. Available since PHP 5.1
date_default_timezone_set('UTC');


// Prints something like: Monday
echo date("l");

// Prints something like: Monday 8th of August 2005 03:12:46 PM
echo date('l jS \of F Y h:i:s A');

// Prints: July 1, 2000 is on a Saturday
echo "July 1, 2000 is on a " . date("l", mktime(0, 0, 0, 7, 1, 2000));

/* use the constants in the format parameter */
// prints something like: Mon, 15 Aug 2005 15:12:46 UTC
echo date(DATE_RFC822);

// prints something like: 2000-07-01T00:00:00+00:00
echo date(DATE_ATOM, mktime(0, 0, 0, 7, 1, 2000));
?>

You can prevent a recognized character in the format string from being expanded by escaping it with a preceding backslash. If the character with a backslash is already a special sequence, you may need to also escape the backslash.

Example #6 Escaping characters in date()

<?php
// prints something like: Wednesday the 15th
echo date('l \t\h\e jS');
?>

It is possible to use date() and mktime() together to find dates in the future or the past.

Example #7 date() and mktime() example

<?php
$tomorrow  = mktime(0, 0, 0, date("m")  , date("d")+1, date("Y"));
$lastmonth = mktime(0, 0, 0, date("m")-1, date("d"),   date("Y"));
$nextyear  = mktime(0, 0, 0, date("m"),   date("d"),   date("Y")+1);
?>

Note:

This can be more reliable than simply adding or subtracting the number of seconds in a day or month to a timestamp because of daylight saving time.

Some examples of date() formatting. Note that you should escape any other characters, as any which currently have a special meaning will produce undesirable results, and other characters may be assigned meaning in future PHP versions. When escaping, be sure to use single quotes to prevent characters like \n from becoming newlines.

Example #8 date() Formatting

<?php
// Assuming today is March 10th, 2001, 5:16:18 pm, and that we are in the
// Mountain Standard Time (MST) Time Zone

$today = date("F j, Y, g:i a");                 // March 10, 2001, 5:16 pm
$today = date("m.d.y");                         // 03.10.01
$today = date("j, n, Y");                       // 10, 3, 2001
$today = date("Ymd");                           // 20010310
$today = date('h-i-s, j-m-y, it is w Day');     // 05-16-18, 10-03-01, 1631 1618 6 Satpm01
$today = date('\i\t \i\s \t\h\e jS \d\a\y.');   // it is the 10th day.
$today = date("D M j G:i:s T Y");               // Sat Mar 10 17:16:18 MST 2001
$today = date('H:m:s \m \i\s\ \m\o\n\t\h');     // 17:03:18 m is month
$today = date("H:i:s");                         // 17:16:18
?>

To format dates in other languages, you should use the setlocale() and strftime() functions instead of date().

注释

Note:

To generate a timestamp from a string representation of the date, you may be able to use strtotime(). Additionally, some databases have functions to convert their date formats into timestamps (such as MySQL's » UNIX_TIMESTAMP function).

Tip

Timestamp of the start of the request is available in $_SERVER['REQUEST_TIME'] since PHP 5.1.

参见

Date/Time 函数
在线手册：中文 英文
PHP手册
PHP手册 - N: 格式化一个本地时间／日期

用户评论:

matt (24-Mar-2012 06:23)

date() has some strange behavior at extremely high values:

<?php
echo "9223372036854775805: " . date("Y-m-d g:i:s a",  9223372036854775805) . "\n";
echo "9223372036854775806: " . date("Y-m-d g:i:s a",  9223372036854775806) . "\n";
echo "9223372036854775807: " . date("Y-m-d g:i:s a",  9223372036854775807) . " (0x7FFFFFFFFFFFFFFF)\n";
echo "9223372036854775808: " . date("Y-m-d g:i:s a",  9223372036854775808) . "\n";
echo "9223372036854775809: " . date("Y-m-d g:i:s a",  9223372036854775809) . "\n";
echo "9223372036854775810: " . date("Y-m-d g:i:s a",  9223372036854775810) . "\n";
echo "...\n";
echo "9223372036854776832: " . date("Y-m-d g:i:s a",  9223372036854776832) . "\n";
echo "9223372036854776833: " . date("Y-m-d g:i:s a",  9223372036854776833) . "\n";
echo "...\n";
echo "9223372036854778879: " . date("Y-m-d g:i:s a",  9223372036854778879) . "\n";
echo "9223372036854778880: " . date("Y-m-d g:i:s a",  9223372036854778880) . "\n";
echo "...\n";
echo "9223372036854780928: " . date("Y-m-d g:i:s a",  9223372036854780928) . "\n";
echo "9223372036854780929: " . date("Y-m-d g:i:s a",  9223372036854780929) . "\n";
echo "...\n";
echo "9223372036854782975: " . date("Y-m-d g:i:s a",  9223372036854782975) . "\n";
echo "9223372036854782976: " . date("Y-m-d g:i:s a",  9223372036854782976) . "\n";
echo "...\n";
echo "9223372036854785024: " . date("Y-m-d g:i:s a",  9223372036854785024) . "\n";
echo "9223372036854785025: " . date("Y-m-d g:i:s a",  9223372036854785025) . "\n";
echo "...\n";
echo "9223372036854787071: " . date("Y-m-d g:i:s a",  9223372036854787071) . "\n";
echo "9223372036854787072: " . date("Y-m-d g:i:s a",  9223372036854787072) . "\n";
echo "...\n";
echo "9223372036854789120: " . date("Y-m-d g:i:s a",  9223372036854789120) . "\n";
echo "9223372036854789121: " . date("Y-m-d g:i:s a",  9223372036854789121) . "\n";
echo "...\n";
echo "9223372036854791167: " . date("Y-m-d g:i:s a",  9223372036854791167) . "\n";
echo "9223372036854791168: " . date("Y-m-d g:i:s a",  9223372036854791168) . "\n";
echo "...\n";
echo "9223372036854793215: " . date("Y-m-d g:i:s a",  9223372036854793215) . "\n";
echo "9223372036854793216: " . date("Y-m-d g:i:s a",  9223372036854793216) . "\n";
echo "9223372036854793217: " . date("Y-m-d g:i:s a",  9223372036854793217) . "\n";
echo "9223372036854793218: " . date("Y-m-d g:i:s a",  9223372036854793218) . "\n";
?>

Output:

9223372036854775805: 292277026596-12-04 10:30:05 am
9223372036854775806: 292277026596-12-04 10:30:06 am
9223372036854775807: 292277026596-12-04 10:30:07 am (0x7FFFFFFFFFFFFFFF)
9223372036854775808: 292277026596-12-04 10:30:08 am
9223372036854775809: 292277026596-12-04 10:30:08 am
9223372036854775810: 292277026596-12-04 10:30:08 am
...
9223372036854778879: 292277026596-12-04 10:30:08 am
9223372036854778880: 292277026596-12-04 11:04:16 am
...
9223372036854778879: 292277026596-12-04 11:04:16 am
9223372036854778880: 292277026596-12-04 11:38:24 am
...
9223372036854780928: 292277026596-12-04 11:38:24 am
9223372036854780929: 292277026596-12-04 12:12:32 pm
...
9223372036854782975: 292277026596-12-04 12:12:32 pm
9223372036854782976: 292277026596-12-04 12:46:40 pm
...
9223372036854785024: 292277026596-12-04 12:46:40 pm
9223372036854785025: 292277026596-12-04 1:20:48 pm
...
9223372036854787071: 292277026596-12-04 1:20:48 pm
9223372036854787072: 292277026596-12-04 1:54:56 pm
...
9223372036854789120: 292277026596-12-04 1:54:56 pm
9223372036854789121: 292277026596-12-04 2:29:04 pm
...
9223372036854791167: 292277026596-12-04 2:29:04 pm
9223372036854791168: 292277026596-12-04 3:03:12 pm
...
9223372036854793215: 292277026596-12-04 3:03:12 pm
9223372036854793216: 292277026596-12-04 3:03:12 pm
9223372036854793217: -292277022657-01-27 8:37:04 am
9223372036854793218: -292277022657-01-27 8:37:04 am

---

So, the last reliable unix timecode is 9223372036854775808 (0x1000000000000000). Not that you would probably ever need a date that high.

Bas Vijfwinkel (19-Mar-2012 02:47)

Note that some formatting options are different from MySQL.
For example using a 24 hour notation without leading zeros is the option '%G' in PHP but '%k' in MySQL.
When using dynamically generated date formatting string, be careful to generate the correct options for either PHP or MySQL.

bakerj417 at gmail dot com (08-Mar-2012 12:48)

If you are having an issue getting u to work so is everyone else. The solution that I am using which I found on another site(so not taking credit) is to use this:

     date("Y/m/d H:i:s"). substr((string)microtime(), 1, 6);

that will give you:

     yyyy/mm/dd hh:ii:ss.uuuuuu

hope this helps someone in need!

thanks all

Stefan at NOSPAM dot wp dot eu (24-Feb-2012 07:39)

<?php
$czteraz=taketime();
$a229=date("t",$czteraz);
$dz_tyd=date("w", $czteraz);
$dz_mie=date("m", $czteraz);
$dz_rok=date("Y", $czteraz);

echo '<hr>kalendarz<br><form>';
echo '<select name="bry20" size="1">';   
    for($u = 1; $u < $a229+1;$u++)    {
    echo '<option ';
    if ($u==date("d", $czteraz)) echo 'selected="selected" ';
    echo 'value="'.$u.'">'.$u.'</option>';
                    }
echo '</select>';

echo '<select name="bry21" size="1">';   
    for($u = 1; $u < 13; $u++)    {
    echo '<option ';
    if ($u==$dz_mie) echo 'selected="selected" ';
    echo 'value="'.$u.'">'.$u.'</option>';
                    }
echo '</select>';

echo '<select name="bry22" size="1">';   
    for($u = 1997; $u < 2018; $u++)    {
    echo '<option ';
    if ($u==$dz_rok) echo 'selected="selected" ';
    echo 'value="'.$u.'">'.$u.'</option>';
                    }
echo '</select></form><br><hr>';
?>

gerben at gerbenwijnja dot nl (22-Feb-2012 01:54)

I use the function below to calculate the Unix timestamp of the start of a week. It includes a boolean flag to request a GMT offset instead of the current locale setting.

<?php

function getWeekOffsetTimestamp($year, $week, $useGmt = false) {
        if ($useGmt) {
                // Backup timezone and set to GMT
                $timezoneSettingBackup = date_default_timezone_get();
                date_default_timezone_set("GMT");
        }

        // According to ISO-8601, January 4th is always in week 1
        $halfwayTheWeek = strtotime($year."0104 +".($week - 1)." weeks");

        // Subtract days to Monday
        $dayOfTheWeek = date("N", $halfwayTheWeek);
        $daysToSubtract = $dayOfTheWeek - 1;

        // Calculate the week's timestamp
        $unixTimestamp = strtotime("-$daysToSubtract day", $halfwayTheWeek);

        if ($useGmt) {
                // Reset timezone to backup
                date_default_timezone_set($timezoneSettingBackup);
        }

        return $unixTimestamp;
}

?>

frank at interactinet dot com (16-Feb-2012 06:07)

If you want to compare this week with the same week last year, here is some code to get you the time at the beginning of the week.  You can then add days, hours, etc to get to the day of the week that you want to know about.

<?php
        $time_passed = (date('N')-1)* 24 * 3600; // time since start of week in days
        $startOfWeek = mktime(0,0,0,date('m'),date('d'),date('Y')) - $time_passed;
       
   
        $lastyear = $startOfWeek - 365*24*3600;   

        // make sure time used from last year is the same week of the year   
        $weekdiff = date('W') - date('W',$lastyear);
        if($weekdiff != 0)
        {
            $lastyear = $lastyear + ($weekdiff*7*24*3600);
        }
       
        $lastyear_time_passed = (date('N',$lastyear)-1) * 24 * 3600; // time since start of week in days
       
        $startOfWeek_lastyear = mktime(0,0,0,date('m',$lastyear),date('d',$lastyear),date('Y',$lastyear)) - $lastyear_time_passed;
?>

So now you have the unix time for the start of this week ($startOfWeek), and the start of the same week last year ($startOfWeek_lastyear).

You can convert back to datetime format easily:

<?php
        echo date('Y-m-d H:i:s',$startOfWeek).'<br>';
        echo date('Y-m-d H:i:s',$startOfWeek_lastyear).'<br><br>';
       
        echo date('l F jS, Y',$startOfWeek).'<br>';
        echo date('l F jS, Y',$startOfWeek_lastyear);
?>

Jimmy (22-Dec-2011 01:04)

Things to be aware of when using week numbers with years.

<?php
echo date("YW", strtotime("2011-01-07")); // gives 201101
echo date("YW", strtotime("2011-12-31")); // gives 201152
echo date("YW", strtotime("2011-01-01")); // gives 201152 too
?>

BUT

<?php
echo date("oW", strtotime("2011-01-07")); // gives 201101
echo date("oW", strtotime("2011-12-31")); // gives 201152
echo date("oW", strtotime("2011-01-01")); // gives 201052 (Year is different than previous example)
?>

Reason:
Y is year from the date
o is ISO-8601 year number
W is ISO-8601 week number of year

Conclusion:
if using 'W' for the week number use 'o' for the year.

blinov vyacheslav AT gmail.com (23-Aug-2011 03:06)

It was oblivious and discouraging that it dont mentioned in docs. If you will use W to get week number be aware:
first days of year can be in a week of previous year, and week number always has leading zero

<?php

echo date("YW", strtotime("2011-01-07")); // gives 201101
echo date("YW", strtotime("2011-01-01")); // gives 201152
echo date("YW", strtotime("2011-12-31")); // gives 201152 too

?>

so you can`t rely on number of week given from this function inside your program if you want to use it for some logic

ghotinet (13-Dec-2010 06:06)

Most spreadsheet programs have a rather nice little built-in function called NETWORKDAYS to calculate the number of business days (i.e. Monday-Friday, excluding holidays) between any two given dates. I couldn't find a simple way to do that in PHP, so I threw this together. It replicates the functionality of OpenOffice's NETWORKDAYS function - you give it a start date, an end date, and an array of any holidays you want skipped, and it'll tell you the number of business days (inclusive of the start and end days!) between them.

I've tested it pretty strenuously but date arithmetic is complicated and there's always the possibility I missed something, so please feel free to check my math.

The function could certainly be made much more powerful, to allow you to set different days to be ignored (e.g. "skip all Fridays and Saturdays but include Sundays") or to set up dates that should always be skipped (e.g. "skip July 4th in any year, skip the first Monday in September in any year"). But that's a project for another time.

<?php

function networkdays($s, $e, $holidays = array()) {
    // If the start and end dates are given in the wrong order, flip them.   
    if ($s > $e)
        return networkdays($e, $s, $holidays);

    // Find the ISO-8601 day of the week for the two dates.
    $sd = date("N", $s);
    $ed = date("N", $e);

    // Find the number of weeks between the dates.
    $w = floor(($e - $s)/(86400*7));    # Divide the difference in the two times by seven days to get the number of weeks.
    if ($ed >= $sd) { $w--; }        # If the end date falls on the same day of the week or a later day of the week than the start date, subtract a week.

    // Calculate net working days.
    $nwd = max(6 - $sd, 0);    # If the start day is Saturday or Sunday, add zero, otherewise add six minus the weekday number.
    $nwd += min($ed, 5);    # If the end day is Saturday or Sunday, add five, otherwise add the weekday number.
    $nwd += $w * 5;        # Add five days for each week in between.

    // Iterate through the array of holidays. For each holiday between the start and end dates that isn't a Saturday or a Sunday, remove one day.
    foreach ($holidays as $h) {
        $h = strtotime($h);
        if ($h > $s && $h < $e && date("N", $h) < 6)
            $nwd--;
    }

    return $nwd;
}

$start = strtotime("1 January 2010");
$end = strtotime("13 December 2010");

// Add as many holidays as desired.
$holidays = array();
$holidays[] = "4 July 2010";            // Falls on a Sunday; doesn't affect count
$holidays[] = "6 September 2010";        // Falls on a Monday; reduces count by one

echo networkdays($start, $end, $holidays);    // Returns 246

?>

Or, if you just want to know how many work days there are in any given year, here's a quick function for that one:

<?php

function workdaysinyear($y) {
    $j1 = mktime(0,0,0,1,1,$y);
    if (date("L", $j1)) {
        if (date("N", $j1) == 6)
            return 260;
        elseif (date("N", $j1) == 5 or date("N", $j1) == 7)
            return 261;
        else
            return 262;
    }
    else {
        if (date("N", $j1) == 6 or date("N", $j1) == 7)
            return 260;
        else
            return 261;
    }
}

?>

@PeteWilliams (08-Sep-2010 12:29)

If you want to use HTML5's <date> tag, the following code will generate the machine-readable value for the 'datetime' attribute:

<?php

/**
 * formats the date passed into format required by 'datetime' attribute of <date> tag
 * if no intDate supplied, uses current date.
 * @param intDate integer optional
 * @return string
 **/
function getDateTimeValue( $intDate = null ) {

    $strFormat = 'Y-m-d\TH:i:s.uP';
    $strDate = $intDate ? date( $strFormat, $intDate ) : date( $strFormat ) ;
   
    return $strDate;
}

echo getDateTimeValue();

?>

lb at bostontech dot net (30-Nov-2009 07:11)

Not sure why this got ignored the first time, but this is an even simpler way to check leap year:

<?php
function isLeapYear($year)
    { return ((($year%4==0) && ($year%100)) || $year%400==0) ? (true):(false); }
?>

Edward Rudd (05-Oct-2009 08:13)

To actually make use ot the "u" (microsecond) you need to use the DateTime object and not the date() function.

For example

<?php
$t = microtime(true);
$micro = sprintf("%06d",($t - floor($t)) * 1000000);
$d = new DateTime( date('Y-m-d H:i:s.'.$micro,$t) );

print $d->format("Y-m-d H:i:s.u");
?>

Just.Kevin (28-Jul-2009 05:52)

In order to determine if a year is a leap year an earlier poster suggested simply checking to see if the year is a multiple of four:

<?php
function is_leapyear_broken($year = 2004) {
return ($year%4)==0;
}
?>

While this will work for the majority of years it will not work on years that are multiples of 100 but not multiples of 400 i.e.(2100).
A function not using php's date() function that will also account for this small anomaly in leap years:

<?php
function is_leapyear_working($year = 2004) {
    if((($year%4==0) && ($year%100!=0)) || $year%400==0) {
        return true;
    }
    return false;
}
?>

While is_leapyear_working will not return true for the few non-leap years divisible by four I couldn't tell you if this is more or less efficient than using php's date() as an even earlier poster suggested:

<?php
function is_leapyear($year = 2004) {
$is_leap = date('L', strtotime("$year-1-1"));
return $is_leap;
}
?>

eduardo at digmotor dot com dot br (21-Apr-2009 09:34)

Thanks to tcasparr at gmail dot com for the great idea (at least for me) ;)
I changed the code a little to replicate the functionality of date_parse_from_format, once I don't have PHP 5.3.0 yet. This might be useful for someone. Hope you don't mind changing your code tcasparr at gmail dot com.

<?php
/*******************************************************
 * Simple function to take in a date format and return array of associated
 * formats for each date element
 *
 * @return array
 * @param string $strFormat
 *
 * Example: Y/m/d g:i:s becomes
 * Array
 * (
 *     [year] => Y
 *     [month] => m
 *     [day] => d
 *     [hour] => g
 *     [minute] => i
 *     [second] => s
 * )
 *
 *  This function is needed for  PHP < 5.3.0
 ********************************************************/
function dateParseFromFormat($stFormat, $stData)
{
    $aDataRet = array();
    $aPieces = split('[:/.\ \-]', $stFormat);
    $aDatePart = split('[:/.\ \-]', $stData);
    foreach($aPieces as $key=>$chPiece)   
    {
        switch ($chPiece)
        {
            case 'd':
            case 'j':
                $aDataRet['day'] = $aDatePart[$key];
                break;
               
            case 'F':
            case 'M':
            case 'm':
            case 'n':
                $aDataRet['month'] = $aDatePart[$key];
                break;
               
            case 'o':
            case 'Y':
            case 'y':
                $aDataRet['year'] = $aDatePart[$key];
                break;
           
            case 'g':
            case 'G':
            case 'h':
            case 'H':
                $aDataRet['hour'] = $aDatePart[$key];
                break;   
               
            case 'i':
                $aDataRet['minute'] = $aDatePart[$key];
                break;
               
            case 's':
                $aDataRet['second'] = $aDatePart[$key];
                break;           
        }
       
    }
    return $aDataRet;
}
?>

Also, if you need to change the format of dates:

<?php
function changeDateFormat($stDate,$stFormatFrom,$stFormatTo)
{
  // When PHP 5.3.0 becomes available to me
  //$date = date_parse_from_format($stFormatFrom,$stDate);
  //For now I use the function above
  $date = dateParseFromFormat($stFormatFrom,$stDate);
  return date($stFormatTo,mktime($date['hour'],
                                    $date['minute'],
                                    $date['second'],
                                    $date['month'],
                                    $date['day'],
                                    $date['year']));
}

?>

Kenneth Kin Lum (02-Oct-2008 11:52)

date(DATE_RFC822) and date(DATE_RFC2822) both work.  note that RFC 822 is obsoleted by RFC 2822.  The main difference is the year being 08 in RFC 822 and is 2008 in RFC 2822.

To use date(DATE_RFC2822), a short form is date('r').

Anonymous (12-Sep-2008 02:01)

Correct format for a MySQL DATETIME column is
<?php $mysqltime = date ("Y-m-d H:i:s", $phptime); ?>

JonathanCross.com (25-Jul-2008 09:22)

<?php
// A demonstration of the new DateTime class for those
// trying to use dates before 1970 or after 2038.
?>
<h2>PHP 2038 date bug demo (php version <?php echo phpversion(); ?>)</h1>
<div style='float:left;margin-right:3em;'>
<h3>OLD Buggy date()</h3>
<?php
  $format='F j, Y';
  for ( $i = 1900; $i < 2050; $i++) {
    $datep = "$i-01-01";
    ?>
    Trying: <?php echo $datep; ?> = <?php echo date($format, strtotime($datep)); ?><br>
    <?php
  }
?></div>
<div style='float:left;'>
  <h3>NEW DateTime Class (v 5.2+)</h3><?php
  for ( $i = 1900; $i < 2050; $i++) {
    $datep = "$i-01-01";
    $date = new DateTime($datep);
    ?>
    Trying: <?php echo $datep; ?> = <?php echo $date->format($format); ?><br>
    <?php
  }
?></div>

phil dot taylor at enilsson dot com (26-May-2008 06:37)

Found this helpful when converting unix dates for use with the ical file format.

<?php
// Converts a unix timestamp to iCal format (UTC) - if no timezone is
// specified then it presumes the uStamp is already in UTC format.
// tzone must be in decimal such as 1hr 45mins would be 1.75, behind
// times should be represented as negative decimals 10hours behind
// would be -10
       
    function unixToiCal($uStamp = 0, $tzone = 0.0) {
   
        $uStampUTC = $uStamp + ($tzone * 3600);       
        $stamp  = date("Ymd\THis\Z", $uStampUTC);
       
        return $stamp;       

    }
?>

chubby at chicks dot com (23-May-2008 02:54)

<?php
/**
     * Checks wether a date is between an interval
     *
     * Usage:
     *     
     * // check if today is older than 2008/12/31
     * var_dump(currentDayIsInInterval('2008/12/31'));
     * // check if today is younger than 2008/12/31
     * var_dump(currentDayIsInInterval(null,'2008/12/31'));
     * // check if today is between 2008/12/01 and 2008/12/31
     * var_dump(currentDayIsInInterval('2008/12/01','2008/12/31')); 
     *
     * Will trigger errors if date is in wrong format, notices if $begin > $end    
     *         
     * @param string $begin Date string as YYYY/mm/dd
     * @param string $end Date string as YYYY/mm/dd
     * @return bool 
     */
function currentDayIsInInterval($begin = '',$end = '')
{
        $preg_exp = '"[0-9][0-9][0-9][0-9]/[0-9][0-9]/[0-9][0-9]"';
        $preg_error = 'Wrong parameter passed to function '.__FUNCTION__.' : Invalide date
format. Please use YYYY/mm/dd.';
        $interval_error = 'First parameter in '.__FUNCTION__.' should be smaller than
second.';
        if(empty($begin))
        {
                $begin = 0;
        }
        else
        {
                if(preg_match($preg_exp,$begin))
                {
                        $begin = (int)str_replace('/','',$begin);
                }
                else
                {
                        trigger_error($preg_error,E_USER_ERROR);
                }
        }
        if(empty($end))
        {
                $end = 99999999;
        }
        else
        {
                if(preg_match($preg_exp,$end))
                {
                        $end = (int)str_replace('/','',$end);
                }
                else
                {
                        trigger_error($preg_error,E_USER_ERROR);
                }
        }
        if($end < $begin)
        {
                trigger_error($interval_error,E_USER_WARNING);
        }
        $time = time();
        $now = (int)(date('Y',$time).date('m',$time).date('j',$time));
        if($now > $end or $now < $begin)
        {
                return false;
        }
        return true;
}
?>

jc (31-Dec-2007 02:28)

date("W") returns the iso8601 week number, while date("Y") returns the _current_ year. This can lead to odd results. For example today (dec 31, 2007) it returns 1 for the week and of course 2007 for the year. This is not wrong in a strict sense because iso defines this week as the first of 2008 while we still have 2007.

So, if you don't have another way to safely retrieve the year according to the iso8061 week-date - strftime("%G") doesn't work on some systems -, you should be careful when working with date("W").

For most cases strftime("%W") should be a safe replacement.

[edit: Much easier is to use "o" (lower case O) instead of "Y"]

mel dot boyce at gmail dot com (06-Apr-2006 12:46)

I've been flicking through the comments looking for some succinct date code and have noticed an alarming number of questions and over-burdened examples related to date mathematics. One of the most useful skills you can utilize when performing date math is taking full advantage of the UNIX timestamp. The UNIX timestamp was built for this kind of work.

An example of this relates to a comment made by james at bandit-dot-co-dot-en-zed. James was looking for a way to calculate the number of days which have passed since a certain date. Rather than using mktime() and a loop, James can subtract the current timestamp from the timestamp of the date in question and divide that by the number of seconds in a day:
<?php
$days = floor((time() - strtotime("01-Jan-2006"))/86400);
print("$days days have passed.\n");
?>

Another usage could find itself in a class submitted by Kyle M Hall which aids in the creation of timestamps from the recent past for use with MySQL. Rather than the looping and fine tuning of a date, Kyle can use the raw UNIX timestamps (this is untested code):
<?php
$ago = 14; // days
$timestamp = time() - ($ago * 86400);
?>

Hopefully these two examples of "UNIX-style" timestamp usage will help those finding date mathematics more elusive than it should be.

SpikeDaCruz (09-Mar-2006 07:12)

The following function will return the date (on the Gregorian calendar) for Orthodox Easter (Pascha).  Note that incorrect results will be returned for years less than 1601 or greater than 2399. This is because the Julian calendar (from which the Easter date is calculated) deviates from the Gregorian by one day for each century-year that is NOT a leap-year, i.e. the century is divisible by 4 but not by 10.  (In the old Julian reckoning, EVERY 4th year was a leap-year.)

This algorithm was first proposed by the mathematician/physicist Gauss.  Its complexity derives from the fact that the calculation is based on a combination of solar and lunar calendars.

<?php
function getOrthodoxEaster($date){
  /*
   Takes any Gregorian date and returns the Gregorian
   date of Orthodox Easter for that year.
  */
  $year = date("Y", $date);
  $r1 = $year % 19;
  $r2 = $year % 4;
  $r3 = $year % 7;
  $ra = 19 * $r1 + 16;
  $r4 = $ra % 30;
  $rb = 2 * $r2 + 4 * $r3 + 6 * $r4;
  $r5 = $rb % 7;
  $rc = $r4 + $r5;
  //Orthodox Easter for this year will fall $rc days after April 3
  return strtotime("3 April $year + $rc days");
}
?>