Helpful strtotime reminders

July 11th, 2007 by Aaron

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Today, Todd [one of the consultants that ("the triangle") uses] called me up to share a bit of a reminder and also tell me about an issue in the code that was in one of our older modules. There was an issue with the strtotime function converting a year to a timestamp.

I thought I’d take a few minutes to just outline strtotime examples again, as a reminder:

Strtotime is a useful function that converts english based strings to unix timestamps. These can range from iso date formats (”2007-07-11″) to proper written dates (’July 11th, 2007′) to descriptive range based dates (”+3 days”). The output is always a unix timestamp compatible with the date() functions. While the manual doesn’t give all the possible combinations, it does give some useful examples. Well, in order to test and predict the behavior of this tool, I tried out a few more date combinations to see what would happen.

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print "date('r', strtotime('now'))";
print date('r', strtotime('now'));
print "<hr />";
 
print "date('r', strtotime('+1 day'))";
print date('r', strtotime('+1 day'));
print "<hr />";
 
print "date('r', strtotime('06/28/1983'))";
print date('r', strtotime('06/28/1983'));
print "<hr />";
 
print "date('r', strtotime('6/28/83'))";
print date('r', strtotime('6/28/83'));
print "<hr />";
 
print "date('r', strtotime('6/1999'))";
print date('r', strtotime('6/1999'));
print "<hr />";
 
print "date('r', strtotime('1999'))";
print date('r', strtotime('1999'));
print "<hr />";

This was the output:( with php 5.2)

date(’r', strtotime(’now’))Wed, 11 Jul 2007 19:05:18 -0500

I wasn’t entirely certain of the second from last result however. I did a quick check, however…. date(’r', 0) comes back as the same time - so thats the proper value for a zero - or unknown date.

Another cool note is that for versions of PHP less than 5.1, they did not support a negative timestamp on windows and some *nix distros. My version on windows have moved pass this limitation though:

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print date('r', -100);

The output:
Wed, 31 Dec 1969 17:58:20 -0600

As always, there is a wealth of knowledge in the comments on the PHP manual page.

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Tags: PHP

This entry was posted on Wednesday, July 11th, 2007 at 7:32 pm and is filed under PHP. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

One Response to “Helpful strtotime reminders”

1. Todd Says:
   June 12th, 2008 at 4:16 pm

   >> Finally, the plain year came out as that year’s version of
   >> today’s date - which is kind of helpful (in case you wanted
   >> to know what day july 11th was back in 1999).

   Be careful when using strtotime with numbers only! gnu wants to interpret number only formats differently and a four-digit number is assumed to be hhmm. Since 1999 is not a valid time (19:99) it must automatically fallback to assuming it is a year, but 2000 is 8:00 p.m. of the current date, watch what happens!

   print “date(’r', strtotime(’1999′))”;
   print date(’r', strtotime(’1999′)) . “\n”;
   print “date(’r', strtotime(’2000′))”;
   print date(’r', strtotime(’2000′)) . “\n”;
   print “date(’r', strtotime(’2230′))”;
   print date(’r', strtotime(’2230′)) . “\n”;

   Prints:

   date(’r', strtotime(’1999′))Sat, 12 Jun 1999 21:36:27 +0000
   date(’r', strtotime(’2000′))Thu, 12 Jun 2008 20:00:00 +0000
   date(’r', strtotime(’2230′))Thu, 12 Jun 2008 22:30:00 +0000

   Note that the date for the last two entries are for 2008, not the years 2000 and 2230, respectively. However, the time is 20:00 and 22:30, respectively. So, the strtotime library views a 4-digit number differently!

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