3.5.4 Durations and time values

If you want to compute time values use the ‘T’, ‘t’, or ‘U’ flag, either in Calc formulas or Elisp formulas:

|  Task 1 |   Task 2 |    Total |
|    2:12 |     1:47 | 03:59:00 |
|    2:12 |     1:47 |    03:59 |
| 3:02:20 | -2:07:00 |     0.92 |
#+TBLFM: @2$3=$1+$2;T::@3$3=$1+$2;U::@4$3=$1+$2;t

Input duration values must be of the form ‘HH:MM[:SS]’, where seconds are optional. With the ‘T’ flag, computed durations are displayed as ‘HH:MM:SS’ (see the first formula above). With the ‘U’ flag, seconds are omitted so that the result is only ‘HH:MM’ (see second formula above). Zero-padding of the hours field depends upon the value of the variable org-table-duration-hour-zero-padding.

With the ‘t’ flag, computed durations are displayed according to the value of the option org-table-duration-custom-format, which defaults to hours and displays the result as a fraction of hours (see the third formula in the example above).

Negative duration values can be manipulated as well, and integers are considered as seconds in addition and subtraction.