The figure programs divide a time in days by named constants –
days_per_week, days_per_month, days_per_year – not by numbers
written in each program, so a company sets them once (a study's
setup: tflplanner writes them from its company standards). These are
the values used where none is set: the figure setup
(tfl_fig_setup_code()) and a figure script of its own define a
constant only when it is not defined yet. The programs say the name as
it is (AVAL / days_per_month): a data column must not be named like
one (tflplanner's review says so).