[R] as.POSIXct problem?

Peter Dalgaard BSA p.dalgaard at biostat.ku.dk
Sat Jan 4 00:53:03 CET 2003

<ripley at stats.ox.ac.uk> writes:

> Can you supply us with details?  For the ISO C99 standard actually says
> The mktime function returns the specified calendar time encoded as a value
> of type time_t. If the calendar time cannot be represented, the function
> returns the value (time_t)-1.
> and that is the behaviour that R expects.  Note that POSIX specifies what
> time_t is, but ISO C does not, so I am at a loss as to how this can be
> `more compliant with the ISO C standard'.

Just do a Google groups search for "mktime glibc" and the whole mess
turns up, including some pretty irate postgresql developers...

The spec in question appears to be


although that doesn't actually mention mktime(), it just talks about
the definition of "Seconds Since the Epoch". The actual definition is


One particular piece of sillyness with mktime() is that it uses a
return value of -1 to signal error, leaving you with a problem for
1969-12-31 23:59:59 UTC if you allow extension to times before the

   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907

More information about the R-help mailing list