Org table date arithmetic with Lisp expressions

Question

It's easy to do date arithmetic using org-mode table formulas. For example, if I enter this table:

| [2020-01-01] | |
| [2020-02-01] | |
| [2020-03-01] | |
#+TBLFM: $2=$1+1

...and then do C-c C-c on the formula, the table updates column 2, adding one day to the dates in column 1.

Can this be done using a Lisp formula instead of a calc formula? If so, how?

I see in the org-mode manual that Lisp formulas support various trailing flags to interpret the table cells in different formats, but not datestamps. I experimented with calc-eval, but calc datestamps differ in format from org datestamps. It appears there's some invisible plumbing that connects the two.

Answer 1

You can use org-table-eval-formula to do the calculation in-place of the field and then retrieve the field value which the lisp form must return with org-table-get-field. In that way you can evaluate the calc formula within your lisp form.

In lisp formulae $1 delivers a string "[2020-01-01]" for the date [2020-01-01]. Therefore the somewhat awkward construction of the calc formula (concat $1 "+1").

See the following example:

| [2020-01-01] |  |
| [2020-02-01] |  |
| [2020-03-01] |  |
#+TBLFM: $2='(progn (org-table-eval-formula nil (concat $1 "+1") t t t t) (org-table-get-field))

---

In this special case where you really only want date calculation you can also use the following Elisp formula instead:

| [2020-01-01] | [2020-01-02] |
| [2020-02-01] | [2020-02-02] |
| [2020-03-01] | [2020-03-02] |
#+TBLFM: $2='(org-format-time-string "[%F]" (org-time-from-absolute (1+ (org-time-string-to-absolute $1))))