RE: Calculating months between two dates

There was a function to do this in earlier XSLT 2.0 drafts -
subtract-dates-yielding-yearMonthDuration or some such - but it was removed
because of difficulties in defining exactly what it should do.

One possible algorithm, which you can easily implement as a function, is

(year-from-date($d1) - year-from-date($d2))*12
+ (month-from-date($d1) - month-from-date($d2))
- if (days-from-date($d1) ge days-from-date($d2)) then 0 else 1

That works reasonably for $d2 < $d1. To handle $d1 < $d2 one approach is to
use the same formula as above, another is to return -($d2 - $d1). For
2007-05-31 - 2007-06-01 one approach gives you -1, the other gives you 0.

Another algorithm is to ignore the day entirely, and just use the year and
month components. Or you can divide the day by the number of days in that
month...

Michael Kay
http://www.saxonica.com/


> -----Original Message-----
> From: Ryan Puddephatt [mailto:rpuddephatt@xxxxxxxxxxxx] 
> Sent: 01 June 2007 19:52
> To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx
> Subject:  Calculating months between two dates
> 
> Hi,
>     I want to know if it is possible to calculate the number 
> of months between two dates. For example 
> xs:duration(xs:date('2009-09-23') -
> current-date())
> 
>  From this I get a result in days, is there a way to convert 
> this or change its result?
> 
> Thanks
> 
> Ryan
> -- 
> 
> Ryan Puddephatt
> Software Engineer
>  
> Teleflex Group - IT UK
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