seq.Date <-
##  enhances base R seq.Date function by allowing the 
##  end.end convention for monthly sequences
function (from, to, by, length.out = NULL, along.with = NULL, end.end = FALSE,
    ...) 
{
    if (missing(from)) 
        stop("'from' must be specified")
    if (!inherits(from, "Date")) 
        stop("'from' must be a Date object")
    if (length(as.Date(from)) != 1) 
        stop("'from' must be of length 1")
    if (!missing(to)) {
        if (!inherits(to, "Date")) 
            stop("'to' must be a Date object")
        if (length(as.Date(to)) != 1) 
            stop("'to' must be of length 1")
    }
    if (!missing(along.with)) {
        length.out <- length(along.with)
    }
    else if (!missing(length.out)) {
        if (length(length.out) != 1) 
            stop("'length.out' must be of length 1")
        length.out <- ceiling(length.out)
    }
    status <- c(!missing(to), !missing(by), !is.null(length.out))
    if (sum(status) != 2) 
        stop("exactly two of 'to', 'by' and 'length.out' / 'along.with' must be specified")
    if (missing(by)) {
        from <- unclass(as.Date(from))
        to <- unclass(as.Date(to))
        res <- seq.default(from, to, length.out = length.out)
        return(structure(res, class = "Date"))
    }
    if (length(by) != 1) 
        stop("'by' must be of length 1")
    valid <- 0
    if (inherits(by, "difftime")) {
        by <- switch(attr(by, "units"), secs = 1/86400, mins = 1/1440, 
            hours = 1/24, days = 1, weeks = 7) * unclass(by)
    }
    else if (is.character(by)) {
        by2 <- strsplit(by, " ", fixed = TRUE)[[1]]
        if (length(by2) > 2 || length(by2) < 1) 
            stop("invalid 'by' string")
        valid <- pmatch(by2[length(by2)], c("days", "weeks", 
            "months", "years"))
        if (is.na(valid)) 
            stop("invalid string for 'by'")
        if (valid <= 2) {
            by <- c(1, 7)[valid]
            if (length(by2) == 2) 
                by <- by * as.integer(by2[1])
        }
        else by <- if (length(by2) == 2) 
            as.integer(by2[1])
        else 1
    }
    else if (!is.numeric(by)) 
        stop("invalid mode for 'by'")
    if (is.na(by)) 
        stop("'by' is NA")
    if (valid <= 2) {
        from <- unclass(as.Date(from))
        if (!is.null(length.out)) 
            res <- seq.default(from, by = by, length.out = length.out)
        else {
            to <- unclass(as.Date(to))
            res <- seq.default(0, to - from, by) + from
        }
        return(structure(res, class = "Date"))
    }
    else {
        r1 <- as.POSIXlt(from)
        if (valid == 4) {
            if (missing(to)) {
                yr <- seq(r1$year, by = by, length = length.out)
            }
            else {
                to <- as.POSIXlt(to)
                yr <- seq(r1$year, to$year, by)
            }
            r1$year <- yr
### begin FP addenda
	    if (end.end && r1$mon==1 && r1$mday>27) {
	       	natyr <- r1$year+1900
		leap <- natyr %% 4 == 0 & 
		     (natyr %% 100 != 0 | natyr %% 400 == 0) ## thx Diethelm Wuertz
		if (r1$mday==28 && !leap[1]) {
		     r1$mday <- r1$mday + leap  
            	}
		if (r1$mday==29 && leap[1]) {
		     r1$mday <- r1$mday - !leap
		}
            }
### end FP addenda            
            res <- .Internal(POSIXlt2Date(r1))
        }
        else if (valid == 3) {
            if (missing(to)) {
                mon <- seq(r1$mon, by = by, length = length.out)
            }
            else {
                to <- as.POSIXlt(to)
                mon <- seq(r1$mon, 12 * (to$year - r1$year) + 
                  to$mon, by)
            }
            r1$mon <- mon
### begin FP addenda
	     if (end.end && r1$mday>27) {
	     	natyr <- r1$year + 1900 + r1$mon %/% 12
		leap <- natyr %% 4 == 0 & 
		     (natyr %% 100 != 0 | natyr %% 400 == 0) ## thx Diethelm Wuertz
            	last <- c(31,28,31,30,31,30,31,31,30,31,30,31)[r1$mon %% 12 + 1]
            	last <- last + (last == 28)*(leap)
            	if (last[1] == r1$mday) {
            		r1$mday <- last
            	}
            	else r1$mday <- pmin(last, r1$mday) ## thx Gabor Grothendieck
            }
### end FP addenda            
            res <- .Internal(POSIXlt2Date(r1))
        }
        return(res)
    }
}