On 31 January 2006 13:13, Barry Krein wrote:
> Ford, Mike wrote:
>
> >
> > Because 1 month from 31-Jan is 31-Feb -- which is taken to
> mean 02-Mar, hence the output of date("M" ...).
> >
> > 2 months from now is 31-Mar, which is ok; 3 months from now
> would be 31-Apr, which would likewise be taken to mean 01-May.
> >
> > This is all as expected -- no bug here.
> >
> > Cheers!
> >
> > Mike
> >
> so the 31 feb would be 30 days right?
> and since +1 month would be 2nd march wouldnt be +2 month
> then 2nd april?
> Sinze its 2nd march +1 month
>
> see ->
> echo strftime("%d %m %Y",strtotime ("+1
> Month",mktime(13,0,0,3,2,2006)))."\n";
>
> ^^ gives 2nd april! ^^
>
> echo "date 1:".strftime("%d %m %Y",strtotime ("+1
> Month",strtotime("+1 Month")))."\n";
>
> ^^ gives 3rd april ^^
Uhm -- my mistake, sorry -- 31st Feb equates to 3rd March, not 2nd, so 3rd April here is correct.
The basic thing is that strtotime() just uses the same day-of-the-month when calculating in months -- so, on the 31st January, it reckons thus:
+1 month: 31st February -- *doesn't exist* converted to 3rd March
+2 months: 31st March -- OK
+3 months: 31st April -- *doesn't exist* converted to 1st May
+4 months: 31st May -- OK
+5 months: 31st June -- *doesn't exist* converted to 1st July
etc., etc.
So you just have to be careful when calculating next/previous months to allow for strangeness like this near the end of a month -- just as you have to watch out for DST transitions if calculating with times near 01:00/02:00/03:00. If all you're interested in is the actual month, your best bet is to normalize to a date that exists in every month (such as 1st) before doing your next/previous calculation.
HTH
Cheers!
Mike
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