tojulian {CTFS} | R Documentation

## Converts Calendar Dates to Julian Dates and Back

### Description

These two functions can be used to convert dates to and from julian formats for computations. There are many functions that do this but these are useful for CTFS. The functions rely upon functions found in the R package survival.

### Usage

    tojulian(x, dateform = "%m/%d/%Y", centurycut = 2020)
    fromjulian(j, dateform = "%m/%d/%Y")

### Arguments

`x` | calendate date in the default format “m/d/yyyy”. The year should be specified with the century included, eg. “12/4/1999”
`j` | the number of days since 1/1/1960
`dateform` | format for calendar date, see `strptime` for format information
`centurycut` | years after this date are assumed to be in the 21st century

### Details

These functions are dependent upon the package survival. They use the functions `mdy.date` and `date.mmddyyy`.

The results of `tojulian` is a number of days, so it is an integer and can be used for computation.

### Value

``tojulian`` | returns an integer, the number of days since 1/1/1960 formatted as d/m/y where d = day, m = 3 letter abreviation for month eg Jan, Feb, Mar..., and y = year.
``fromjulian`` | returns a calendar date in mm/dd/yyyy format

### Author(s)

Rick Condit

### References

depends on the package survival

### See Also

`CTFS.utilities`

### Examples

    ## Not run:
    1.  tojulian()

    x1="3/5/1987"
    x2="3/5/2001"
    y1 <- tojulian(x1)
    y2 <- tojulian(x2)
    str(y1)
    str(y2)
    y2-y1

    2.  fromjulian()
    fromjulian(9925)
    fromjulian(15039)
    fromjulian(y1+(y2-y1))
      ## End(Not run)

[Package CTFS version 1.00 Index]