#### 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.