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    <p>The "add a month", etc., annoyance due to different month lengths is, indeed, irritating.</p> <p>The solution, if you have PHP >= 5.2, is the <a href="http://php.net/manual/en/class.datetime.php" rel="nofollow" title="DateTime class">DateTime class</a>.</p> <p>Though it is simple to use this class to obtain total control, it is not <em>entirely</em> trivial.</p> <p>Here is one version of correct code to add a month.</p> <pre><code>// Variables defining the start date // Example only - this could be any valid date $year = '2013'; $month = '01'; $day = '31'; // set to the desired starting date and time $the_date = new DateTime($year . '-' . $month . '-' . $day); // Jump to the first day of this month $the_date-&gt;modify("first day of this month"); // add 14 days, so we'll land on the 15th $the_date-&gt;add(new DateInterval("P14D")); // add 1 month - guaranteed to work! $the_date-&gt;add(new DateInterval("P1M")); // calculate how many days to add to 15 to get back to the **day** we started with... // (as an integer, regardless of whether it is a valid day of the current month) $number_days_to_add_back = intval($day) - 15; // determine the last day of the month stored in $the_date $test_last_date = clone $the_date; $test_last_date-&gt;modify("last day of this month"); $day_last = $test_last_date-&gt;format('j'); // This provides the day, 01-31 // Test if adding $number_days_to_add_back runs past // the end of the month; if so, adjust it so it won't run past // the last day of the month if (15 + $number_days_to_add_back &gt; intval($day_last)) { $number_days_to_add_back = intval($day_last) - 15; } // Now make the final adjustment $the_date-&gt;modify("" . $number_days_to_add_back . " day"); // Test it - a month has been added $test = date_format($the_date, 'Y-m-d'); </code></pre>
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    1. POAlgorithm for calculating a series of future dates based on a frequency
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    1. USDan Nissenbaum
    1. USDan Nissenbaum
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    1. POAlgorithm for calculating a series of future dates based on a frequency
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    1. COHow would this handle "one month from Jan 31"? Would it stop short to Feb 28 or run over to Mar 3?
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      1. USuser548084
    2. CO@user548084 - I have filled in the code sample with a complete working version from start to finish.
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      1. USDan Nissenbaum
    3. COThis is the best answer, so thank you, but the complexity still seems to be there. I was hoping there would be a library or PHP class that could efficiently handle "2013-01-31".addMonths(3) and correctly resolve that to "2013-04-30", but there is a lot of great use cases in this answer. Thanks.
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