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[2007-01-29 11:20 UTC] slomo at sonarkollektiv dot de
Description: ------------ I was looking for a neat solution for the task "get the date for a given weeknumber and weekyear". I thought I got it, but there is a strange behaviour if (and only if) week no. is 1 and 4th of January is already a monday. See my code to reproduce the results, it's quite confusing. The idea was: - 4th of January is always in week no. 1 - add the missing weeks - make it a monday of that week acording to the GNU Date Input Formats syntax descibed at http://www.gnu.org/software/tar/ manual/html_node/tar_114.html#SEC114 So either me or PHP still does not get it right. Reproduce code: --------------- function MondayOfWeek($year, $week) { return strtotime("$year-01-04 UTC + " . ($week-1) . ' week last monday'); } for ($y = 1998; $y < 2012; $y++) { for ($w = 1; $w < 53; $w++) { $start = MondayOfWeek($y, $w); $end = strtotime("+6 day", $start); echo "KW $w/$y: " . gmstrftime('%A, %x %X', $start) . ' - ' . gmstrftime('%A, %x %X', $end) . " "; echo '- reverse check (week/year): ' . gmstrftime('%V/%G', $start) . "\n"; if ($w != gmstrftime('%V', $start) || $y != gmstrftime('%G', $start)) { echo "ERROR!\n"; } } echo "<hr>\n"; } Expected result: ---------------- accurate results for every week number and year with always the same behaviour ... Actual result: -------------- if week no. is 1 and 4th of January is already a monday, the function returns timestamps for the "previous week". PatchesPull RequestsHistoryAllCommentsChangesGit/SVN commits
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Last updated: Thu Nov 20 06:00:01 2025 UTC |
You can also just use "strtotime('2007W011')"; for Monday "1", of Week 1 ("01") of year 2007 ("2007").My "Reproduce code" was quite complete. Here it is again, this time it starts with <?php and ends with ?> :-) I expect: using strtotime("last monday") should behave always the same. If you run my code you will see that it differs depending on the given date. My code is not complex, so I hope you get the point very soon. This "Day of week items" are a little bit confusing, because if you have e.g. a $date for a monday and state strtotime ("$date last monday"), you get $date. I assume this is correct. Anyway I would think it's just my fault if my function would be "off 1 week" for the whole year if the date is a monday every time. But this happens only for the first week, in any other week the result is like I learned strtotime() is doing it. Can you follow? <?php function MondayOfWeek($year, $week) { return strtotime("$year-01-04 UTC + " . ($week-1) . ' week last monday'); } for ($y = 1998; $y < 2012; $y++) { for ($w = 1; $w < 53; $w++) { $start = MondayOfWeek($y, $w); $end = strtotime("+6 day", $start); echo "KW $w/$y: " . gmstrftime('%A, %x %X', $start) . ' - ' . gmstrftime('%A, %x %X', $end) . ' - reverse check (week/year): ' . gmstrftime('%V/%G', $start) . "<br />\n"; if ($w != gmstrftime('%V', $start) || $y != gmstrftime('%G', $start)) { echo '<span style="color: red;">Oops, EXCEPTIONAL ERROR!</span>' . "<br />\n"; } } echo "<hr>\n"; } ?> best regards, slomoCould you please just paste something like this: code : strftime("<something>") actual result: <something you can actually see> expected result: <something you expected to see> I really don't think those functions, cycles and HTML output are required to demonstrate a problem with strftime().code : strtotime('1999-01-04 UTC + 1 week last monday'); strtotime('1999-01-11 UTC + 0 week last monday'); actual result: 916012800 915408000 expected result: at least the same value Another example code : strtotime('1999-01-04 UTC + 0 week last monday'); strtotime('1999-01-04 UTC + 1 week last monday'); strtotime('1999-01-04 UTC + 2 week last monday'); actual result: 914803200 916012800 916617600 expected result: at least always the same gap (604800 is a week), but it differsJust to point out why I think somethings weird, compare the previous code and result to this one. code: strtotime('2000-01-04 UTC + 1 week last monday'); strtotime('2000-01-11 UTC + 0 week last monday'); actual result: 947462400 947462400 expected result: 947462400 947462400 > same value, fine. And the same for code: strtotime('2000-01-04 UTC + 0 week last monday'); strtotime('2000-01-04 UTC + 1 week last monday'); strtotime('2000-01-04 UTC + 2 week last monday'); actual result: 946857600 947462400 948067200 expected result: 946857600 947462400 948067200 > always the same gap (604800 is a week), fine.code : >strtotime('1999-01-04 UTC + 1 week last monday'); >strtotime('1999-01-11 UTC + 0 week last monday'); >actual result: >916012800 >915408000 >expected result: >at least the same value Your expectation is wrong. 1999-01-04 is Monday, so "last monday" for 1999-01-04 is "1999-01-04 minus 1 week" and "last monday" 1999-01-11 is 1999-01-04. >expected result: >at least always the same gap (604800 is a week), but it >differs See previous explanation. No bug here.> Your expectation is wrong. > 1999-01-04 is Monday, so "last monday" for 1999-01-04 is "1999-01-04 > minus 1 week" and "last monday" 1999-01-11 is 1999-01-04. I still do not agree. I expect: code : strtotime("1999-01-04 UTC + 1 week last monday"); strtotime("1999-01-11 UTC + 0 week last monday"); 1999-01-04 is monday 1999-01-11 is monday too If you say: "1999-01-04 UTC + 1 week last monday" means "1999-01-04 minus 1 week" (because 1999-01-04 is monday) you forgot to mention the "+ 1 week" in the expression, this makes "1999-01-04 minus 1 week plus 1 week" for me = 1999-01-04 , or? following you explanation "1999-01-11 UTC + 0 week last monday" then means "1999-01-11 minus 1 week" (because 1999-01-11 is monday too) and again we have to consider "+ 0 week", this makes "1999-01-11 minus 1 week plus 0 week" for me = 1999-01-04 , or do I miss something? Next test: code : strtotime("1999-01-04 UTC + 0 week last monday"); strtotime("1999-01-04 UTC + 1 week last monday"); strtotime("1999-01-04 UTC + 2 week last monday"); actual result: 914803200 916012800 916617600 expected result: at least always the same gap (604800 is a week), but it differs > See previous explanation. > No bug here. This answer is even more confusing for me. 1999-01-04 is monday, correct? no matter how you turn it, either "1999-01-04 last monday" = 1998-12-28 + X weeks = something with always the same gap or "1999-01-04" + X weeks = a date, and a monday too -> now apply "last monday" = something with always the same gap (we are working with a monday, no matter how you turn it, so I expect strtotime() to behave alike, the only differing value is the "+ X weeks") I still expect "something with always the same gap". Sorry for my stubbornness :( At the moment I see that strtotime("1999-01-11 UTC last monday + 1 week") and strtotime("1999-01-11 UTC + 1 week last monday") are giving different results ... now I give up :) Thank you for your support even more for the neat solution using strtotime('2007W011').Ok, I think I got that and I did not claim anything else :-/ Are we talking about your code or my code now? If we are talking about my example comparing strtotime ("1999-01-04 UTC + 1 week last monday") to strtotime ("1999-01-11 UTC + 0 week last monday") someone may fully read or comment my stressed post. If we are talking about the meaning of "1999-01-04 UTC + **0** week last monday" I think we now just agree with each other.