calculate weekday of birthday

calculate weekday of birthday

[Salome Soedergran]

Hi everybody

How can I make orgmode to give me the weekday of a specific date?
I have a list (org-table) with students' names and dates of birth that looks like this:
|------+-----------+------+-------+-----+-----+---------|
| Name | Firstname | year | month | day | age | weekday |
|------+-----------+------+-------+-----+-----+---------|
| Doe  | John      | 2001 |    05 |  21 |  16 |         |
|------+-----------+------+-------+-----+-----+---------|
#+TBLFM: @2$8..@>$6='(+ (- 2017 $5) (if(> $4 7) 0 1));L::

I have a formula to make orgtable calculate the age the student reaches in the current academic year (Aug-July) but I don't know how to get the birthday's weekday in the current year. Can anybody help me? Thanks a lot in advance!

Best, Salome

Re: calculate weekday of birthday

[Adam Porter]

Hi Salome,

The decode-time function returns a list that includes the day-of-week as
a number from 0-6.  You'll have to give it an encoded time, which you
can use encode-time for.

A wild idea would be to use the shell "date" command, which is overkill
for this, but I just happen to have this code handy, in case you or
anyone else might find it useful:

#+BEGIN_SRC elisp
(defmacro call-process-with-args (process &rest args)
  "Return results of running PROCESS with ARGS."
  (declare (indent defun))
  `(with-temp-buffer
     (unless (= 0 (call-process ,process nil t nil
                                ,@args))
       (user-error ,(concat process " failed")))
     (buffer-substring-no-properties (point-min) (point-max))))

(defun get-day-of-week (string)
  "Parse STRING with the shell `date' command and return day-of-week as string."
  (call-process-with-args
   "date" "-d" string "+%a"))
#+END_SRC

Re: calculate weekday of birthday

[Nick Dokos]

Salome Soedergran <salome.soedergran@gmx.ch> writes:

> Hi everybody
>
> How can I make orgmode to give me the weekday of a specific date?
> I have a list (org-table) with students' names and dates of birth that looks like this:
> |------+-----------+------+-------+-----+-----+---------|
> | Name | Firstname | year | month | day | age | weekday |
> |------+-----------+------+-------+-----+-----+---------|
> | Doe  | John      | 2001 |    05 |  21 |  16 |         |
> |------+-----------+------+-------+-----+-----+---------|
>
> #+TBLFM: @2$8..@>$6='(+ (- 2017 $5) (if(> $4 7) 0 1));L::
>
> I have a formula to make orgtable calculate the age the student
> reaches in the current academic year (Aug-July) but I don't know how
> to get the birthday's weekday in the current year. Can anybody help
> me? Thanks a lot in advance!
>
> Best, Salome
>
>

,----
| org-day-of-week is a compiled Lisp function in
| ‘../org-mode/lisp/org-clock.el’.
| 
| (org-day-of-week DAY MONTH YEAR)
| 
| Returns the day of the week as an integer.
`----
You'll have to translate that into a name:

0 = Sunday
...
6 = Saturday

I believe.

-- 
Nick