Hi group, suppose I have a date, say May 15 2004, and I want to now what date it is 23 days before that date. The way to calculate the new date should (...) take account of leap years :) In pseudocode: olddate <- "May 15 2004" newdate <- olddate-23 I looked around in POSIXct etc..., maybe I overlooked? Thanks, Maarten -------------------------------------------------------------- Zie ook/see also: http://www.knmi.nl/maildisclaimer.html
Hoeven, Maarten van der <Maarten.van.der.Hoeven <at> knmi.nl>
writes:
: suppose I have a date, say May 15 2004, and I want to now what date it is 23
days before that date. The way to
: calculate the new date should (...) take account of leap years :)
:
: In pseudocode:
:
: olddate <- "May 15 2004"
: newdate <- olddate-23
:
: I looked around in POSIXct etc..., maybe I overlooked?
as.Date("2005-05-24")-23
On Wed, 26 May 2004, Hoeven, Maarten van der wrote:> suppose I have a date, say May 15 2004, and I want to now what date it > is 23 days before that date. The way to calculate the new date should > (...) take account of leap years :) > > > In pseudocode: > > olddate <- "May 15 2004" > newdate <- olddate-23 > > I looked around in POSIXct etc..., maybe I overlooked?olddate <- as.Date("May 15 2004", "%B %d %Y") newdate <- olddate - 23 newdate [1] "2004-04-22" format(newdate, "%B %d %Y") [1] "April 22 2004" looks straightforward enough to me (and it knows about leap years). -- Brian D. Ripley, ripley at stats.ox.ac.uk Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595