defining a clocktable in a capture template with absolute timespan computed relative to today

[Brian van den Broek <brian.van.den.broek@gmail.com>]

Hi all,

I've been experimenting with a new means of using org to plan my day at
the outset and, at the end of it, to easily review how close I have come
to accomplishing what I planned. For that second component, I want a
clocktable covering the day to allow for an easy review of what I have
accomplished. Since I am an extreme night-owl, I want the table to cover
8:00 of the day to 8:00 of the next one. (Things I do at 0:300 I think of as
having been part of the previous day.) This is easy enough to accomplish
manually. Today's, for instance, is defined as
  #+BEGIN: clocktable :maxlevel 4 :scope agenda :tstart "<2012-04-17
08:00>" :tend "<2012-04-18 Wed 08:00>" :fileskip0

  #+END:

I've defined a capture template to produce, in a datetree, the
boiler-plate for my daily planning and for the end of day review. As
yet, the best I have managed for the clocktable is to include (some
aspects omitted):
  #+BEGIN: clocktable :tstart \"<%(format-time-string \"%Y-%m-%d\"
(current-time)) 08:00>\" :tend \"<%(format-time-string \"%Y-%m-%d\"
(current-time)) 08:00>\" :fileskip0

  #+END:

This still needs some fiddling to get the :tend parameter right as it
defines it as exactly the same as the :tstart.

What I need is something that fulfils the intent of
  :tend \"<%(format-time-string \"%Y-%m-%d\" (+ oneday
(current-time))) 08:00>\".
However, the docstring of (current-time) reads:

  Return the current time, as the number of seconds since 1970-01-01 00:00:00.
  The time is returned as a list of three integers.  The first has the
  most significant 16 bits of the seconds, while the second has the
  least significant 16 bits.  The third integer gives the microsecond
  count.

My meagre elisp means that I will have to spend quite some time figuring
out how to add 1 day to the return value of (current-time).

So:

1) Is there an org-native way that I have overlooked to define a
clock-table in a capture template that has the relative time-span that I
desire?

2) If not, would someone please take pity on my poor elisp and give me
the push to bring home my definition?

Thanks and best,

Brian vdB

PS I suspect that this will wrap badly. Apologies if so; I hope the
intent is nonetheless clear.