How can I get the first week day in a given week number?
I'm making a function in PHP for a calendar app.
The idea: When I click on a link that basically uses strtotime with +1 month it only jumps to that same day of course. I need to get the week numbers correct.
Example: When I use the menu to move from August to September, it shouldn't select the same date I was in in August, but the first day of the first week number in September (Monday, 2th of September, week number 36).
And from September to October: Week number 40, Tuesday the 1th of October.
I found a function that exactly like you want it. This is setISODate
$date = new DateTime();
$date->setISODate(2013, 35, 1);
echo $date->format('Y-m-d');
You can change Y-m-d date format as you want
Output
2013-08-26 // This week number and monday
Usage
setISODate(year, week, day)
Try this code
<?php
$week = 3;
$year = 2009;
$timestamp = mktime( 0, 0, 0, 1, 1, $year ) + ( $week * 7 * 24 * 60 * 60 );
$timestamp_for_monday = $timestamp - 86400 * ( date( 'N', $timestamp ) - 1 );
$date_for_monday = date( 'Y-m-d', $timestamp_for_monday );
?>
Like every1 already said, ISO weeks start with monday. Quote from http://en.wikipedia.org/wiki/ISO_week_date : Weeks start with Monday.
If I understand your problem correctly, you need first-next-date in next month if selected week is in 2 different months?
function getFirstWeekDay($year, $week) {
$dt = (new DateTime)->setISODate($year, $week, 1);
$dtC = clone $dt;
for ($N = $dt->format('N'); $N < 7; $N++) {
$dtC->modify('+1 day');
if ($dt->format('m') !== $dtC->format('m')) {
return $dtC;
}
}
return $dt;
}
echo getFirstWeekDay(2013, 40)->format('W\t\h \w\e\e\k \i\s Y-m-d');
# 40th week is 2013-10-01
echo getFirstWeekDay(2013, 1)->format('W\t\h \w\e\e\k \i\s Y-m-d');
# 1th week is 2013-01-01
Given a Month and a weekday, I need to build a function that can retrieve the day number of all Mondays, Tuesdays, Wednesdays, Thursdays and Fridays.
Let's say I give the function this month, September 2012 and weekday number 1. The function should retrieve all the Mondays in September 2012 which are: 3, 10, 17 and 24
Please note that to me weekday number 1 is Monday, number 2 Tuesday, 3 is Wednesday, 4 Thursday and 5 Friday.
So far I've have done: getting the first day of the week given today's date (I post the function below). But I don't know how to follow from here in a simple way, I've been many hours on it and I suspect there's a better way to do it. Can you please show me how?
function getFirstDayOfWeek($date) {
$getdate = getdate($date);
// How many days ahead monday are we?
switch ( $getdate['wday'] ) {
case 0: // we are on sunday
$days = 6;
break;
default: // any other day
$days = $getdate['wday']-1;
break;
}
$seconds = $days*24*60*60;
$monday = date($getdate[0])-$seconds;
return $monday;
}
Thanks a ton
Not very smart, but would works for you:
// sept. 2012
$month = 9;
// loop through month days
for ($i = 1; $i <= 31; $i++) {
// given month timestamp
$timestamp = mktime(0, 0, 0, $month, $i, 2012);
// to be sure we have not gone to the next month
if (date("n", $timestamp) == $month) {
// current day in the loop
$day = date("N", $timestamp);
// if this is between 1 to 5, weekdays, 1 = Monday, 5 = Friday
if ($day == 1 OR $day <= 5) {
// write it down now
$days[$day][] = date("j", $timestamp);
}
}
}
// to see if it works :)
print_r($days);
I am trying to get an array of a date plus the next 13 dates to get a 14 day schedule starting from a given date.
here is my function:
$time = strtotime($s_row['schedule_start_date']); // 20091030
$day = 60*60*24;
for($i = 0; $i<14; $i++)
{
$the_time = $time+($day*$i);
$date = date('Y-m-d',$the_time);
array_push($dates,$date);
}
But it seems to be repeating a date when the month switches over..
this is what I get:
2009-10-30|2009-10-31|2009-11-01|2009-11-01|2009-11-02|2009-11-03|2009-11-04|2009-11-05|2009-11-06|2009-11-07|2009-11-08|2009-11-09|2009-11-10|2009-11-11
Notice that 2009-11-01 is repeated. I cannot figure out why?
What am I doing wrong?
Thanks!!
I would use strtotime
$start = strtotime($s_row['schedule_start_date']);
$dates=array();
for($i = 1; $i<=14; $i++)
{
array_push($dates,date('Y-m-d', strtotime("+$i day", $start)));
}
print_r($dates);
You have the same date because of daylight saving time switch. It's not safe to add 24*60*60 seconds to find next day, because 2 days in the year have more/less seconds in them. When you switch from summer to winter time you are adding 1 hour to a day. So it'll be 25*60*60 seconds in that day, that's why it's not switched in your code.
You can do your calculation by mktime(). For example:
## calculate seconds from epoch start for tomorrow
$tomorrow_epoch = mktime(0, 0, 0, date("m"), date("d")+1, date("Y"));
## format result in the way you need
$tomorrow_date = date("M-d-Y", $tomorrow_epoch);
Or the full version for your code:
$dates = array();
$now_year = date("Y");
$now_month = date("m");
$now_day = date("d");
for($i = 0; $i < 14; $i++) {
$next_day_epoch = mktime(0, 0, 0, $now_month, $now_day + $i, $now_year);
array_push(
$dates,
date("Y-m-d", $next_day_epoch)
);
}
I recommend something like:
for($i=1;$i<=14;$i++){
echo("$i day(s) away: ".date("m/d/Y",strtotime("+$i days")));
}
I'm trying to write a calendar function like this
function get_date($month, $year, $week, $day, $direction)
{
....
}
$week is a an integer (1, 2, 3...), $day is a day (Sun, Mon, ...) or number, whichever is easier. The direction is a little confusing, because it does a different calculation.
For an example, let's call
get_date(5, 2009, 1, 'Sun', 'forward');
It uses the default, and gets the first Sunday in May ie 2009-05-03. If we call
get_date(5, 2009, 2, 'Sun', 'backward');
, it returns the second last Sunday in May ie 2009-05-24.
The language-agnostic version:
To get the first particular day of the month, start with the first day of the month: yyyy-mm-01. Use whatever function is available to give a number corresponding to the day of the week. Subtract that number from the day you are looking for; for example, if the first day of the month is Wednesday (2) and you're looking for Friday (4), subtract 2 from 4, leaving 2. If the answer is negative, add 7. Finally add that to the first of the month; for my example, the first Friday would be the 3rd.
To get the last Friday of the month, find the first Friday of the next month and subtract 7 days.
Perhaps it can be made quicker...
This was VERY interesting to code.
Please note that $direction is 1 for forward and -1 for backward to ease things up :)
Also, $day begins with a value of 1 for Monday and ends at 7 for Sunday.
function get_date($month, $year, $week, $day, $direction) {
if($direction > 0)
$startday = 1;
else
$startday = date('t', mktime(0, 0, 0, $month, 1, $year));
$start = mktime(0, 0, 0, $month, $startday, $year);
$weekday = date('N', $start);
if($direction * $day >= $direction * $weekday)
$offset = -$direction * 7;
else
$offset = 0;
$offset += $direction * ($week * 7) + ($day - $weekday);
return mktime(0, 0, 0, $month, $startday + $offset, $year);
}
I've tested it with a few examples and seems to work always, be sure to double-check it though ;)
PHP's built-in time functions make this simple.
http://php.net/manual/en/function.strtotime.php
// Get first Friday of next month.
$timestamp = strtotime('first fri of next month');
// Get second to last Friday of the current month.
$timestamp = strtotime('last fri of this month -7 days');
// Format a timestamp as a human-meaningful string.
$formattedDate = date('F j, Y', strtotime('first wed of last month'));
Note that we always want to make sure that we've defined the correct timezone for use with strtotime so that PHP has an understanding of where to compute the timestamp for relative to what time zone the machine thinks it's in.
date_default_timezone_set('America/New_York');
$formattedDate = date('F j, Y', strtotime('first wed of last month +1 week'));
strtotime() can help you. e.g. <?php
$tsFirst = strtotime('2009-04-00 next friday');
$tsLast = strtotime('2009-05-01 last friday');
echo date(DATE_RFC850, $tsFirst), " | ", date(DATE_RFC850, $tsLast);printsFriday, 03-Apr-09 00:00:00 CEST | Friday, 24-Apr-09 00:00:00 CEST
No need for calculations or loops - this is very easy to do with strtotime():
Find the the Nth or Last occurrence of a particular day of a particular a month:
/////////////////////////////////////////////////////////////////
// Quick Code
/////////////////////////////////////////////////////////////////
// Convenience mapping.
$Names = array( 0=>"Sun", 1=>"Mon", 2=>"Tue", 3=>"Wed", 4=>"Thu", 5=>"Fri", 6=>"Sat" );
// Specify what we want
// In this example, the Second Monday of Next March
$tsInMonth = strtotime('March');
$Day = 1;
$Ord = 2;
// The actual calculations
$ThisMonthTS = strtotime( date("Y-m-01", $tsInMonth ) );
$NextMonthTS = strtotime( date("Y-m-01", strtotime("next month", $tsInMonth) ) );
$DateOfInterest = (-1 == $Ord)
? strtotime( "last ".$Names[$Day], $NextMonthTS )
: strtotime( $Names[$Day]." + ".($Ord-1)." weeks", $ThisMonthTS );
/////////////////////////////////////////////////////////////////
// Explanation
/////////////////////////////////////////////////////////////////
// Specify the month of which we are interested.
// You can use any timestamp inside that month, I'm using strtotime for convenience.
$tsInMonth = strtotime('March');
// The day of interest, ie: Friday.
// It can be 0=Sunday through 6=Saturday (Like 'w' from date()).
$Day = 5;
// The occurrence of this day in which we are interested.
// It can be 1, 2, 3, 4 for the first, second, third, and fourth occurrence of the day in question in the month in question.
// You can also use -1 to fine the LAST occurrence. That will return the fifth occurrence if there is one, else the 4th.
$Ord = 3;
////////////////////////////////////////////////////////////////
// We now have all the specific values we need.
// The example values above specify the 3rd friday of next march
////////////////////////////////////////////////////////////////
// We need the day name that corresponds with our day number to pass to strtotime().
// This isn't really necessary = we could just specify the string in the first place, but for date calcs, you are more likely to have the day number than the string itself, so this is convenient.
$Names = array( 0=>"Sun", 1=>"Mon", 2=>"Tue", 3=>"Wed", 4=>"Thu", 5=>"Fri", 6=>"Sat" );
// Calculate the timestamp at midnight of the first of the month in question.
// Remember $tsInMonth is any date in that month.
$ThisMonthTS = strtotime( date("Y-m-01", $tsInMonth ) );
// Calculate the timestamp at midnight of the first of the FOLLOWING month.
// This will be used if we specify -1 for last occurrence.
$NextMonthTS = strtotime( date("Y-m-01", strtotime("next month", $tsInMonth) ) );
// Now we just format the values a bit and pass them to strtotime().
// To find the 1,2,3,4th occurrence, we work from the first of the month forward.
// For the last (-1) occurence,work we work back from the first occurrence of the following month.
$DateOfInterest = (-1 == $Ord) ?
strtotime( "last ".$Names[$Day], $NextMonthTS ) : // The last occurrence of the day in this month. Calculated as "last dayname" from the first of next month, which will be the last one in this month.
strtotime( $Names[$Day]." + ".($Ord-1)." weeks", $ThisMonthTS ); // From the first of this month, move to "next dayname" which will be the first occurrence, and then move ahead a week for as many additional occurrences as you need.
echo date('Y-m-d',strtotime('last friday'));
You can use mktime to retrieve the unix timestamp of the first day in the month:
$firstOfMonth = mktime(0, 0, 0, $month, 1, $year);
When you have the date of the first day of a certain month it's easy to retrieve the weekday for that date using date:
$weekday = date("N", $firstOfMonth);
From there it's rather easy to just step forward to get the date you're after.
function get_date($month, $year, $week, $day) {
# $month, $year: current month to search in
# $week: 0=1st, 1=2nd, 2=3rd, 3=4th, -1=last
# $day: 0=mon, 1=tue, ..., 6=sun
$startday=1; $delta=0;
if ($week < 0) {
$startday = date('t', mktime(0, 0, 0, $month, 1, $year)); # 28..31
$delta=1;
}
$start = mktime(0, 0, 0, $month, $startday, $year);
$dstart = date('w', $start)-1; # last of the month falls on 0=mon,6=sun
$offset=$day-$dstart; if ($offset<$delta){$offset+=7;}
$newday=$startday+$offset+($week*7);
return mktime(0, 0, 0, $month, $newday, $year);
}
This works for me, and based on the language-agnostic version :-)
Only too bad, I needed to do that delta-thing (for if the last day of the month is the wanted week-day, we do not need to subtract 7)
The same can be accomplished very elegantly using the DateTime class.
$time_zone = new DateTimeZone('Europe/Ljubljana');
$first_friday_of_this_month = new DateTime('first Friday of this month', $time_zone);
$last_friday_of_this_month = new DateTime('last Friday of this month', $time_zone);
echo $first_friday_of_this_month->format('Y-m-d'); # 2015-11-06
echo $last_friday_of_this_month->format('Y-m-d'); # 2015-11-27
Just find out what the first and last day of the month in question is (i.e. May 1, 2009 is a Friday and May 31, 2009 is a Sunday) I believe most PHP functions use Monday=0, Sunday=6, thus Friday=4, so you know that Sunday (6) - Friday (4) = 2, then 31-2 = 29, meaning the last friday of this month is on the 29th. For the first Friday, if the number is negative, add 7, if the number is 0, the month starts on Friday.
This seems to work perfect everytime; it takes any date provided and returns the date of the last friday of the month, even in case of 5 friday in the month.
function get_last_friday_of_month($inDate) {
$inDate = date('Y-m-24', strtotime($inDate));
$last_friday = date('Y-m-d',strtotime($inDate.' next friday'));
$next_friday = date('Y-m-d',strtotime($inDate.' next friday'));
if(date('m', strtotime($last_friday)) === date('m', strtotime($next_friday))){
$last_friday = $next_friday;
}else{
//
}
return $last_friday;
}
Below is the quickest solution and you can use in all conditions. Also you could get an array of all day of week if you tweak it a bit.
function findDate($date, $week, $weekday){
# $date is the date we are using to get the month and year which should be a datetime object
# $week can be: 0 for first, 1 for second, 2 for third, 3 for fourth and -1 for last
# $weekday can be: 1 for Monday, 2 for Tuesday, 3 for Wednesday, 4 for Thursday, 5 for Friday, 6 for Saturday and 7 for Sunday
$start = clone $date;
$finish = clone $date;
$start->modify('first day of this month');
$finish->modify('last day of this month');
$finish->modify('+1 day');
$interval = DateInterval::createFromDateString('1 day');
$period = new DatePeriod($start, $interval, $finish);
foreach($period AS $date){
$result[$date->format('N')][] = $date;
}
if($week == -1)
return end($result[$weekday]);
else
return $result[$weekday][$week];
}
$date = DateTime::createFromFormat('d/m/Y', '25/12/2016');
# find the third Wednesday in December 2016
$result = findDate($date, 2, 3);
echo $result->format('d/m/Y');
I hope this helps.
Let me know if you need any further info. ;)