@section Specifying durations

Some tools (@samp{dadd}, @samp{dseq}) need durations as their input.
Durations are generally incompatible with input formats as specified by
@samp{-i|--input-format} and (at the moment) the input syntax is fixed.

The general format is @samp{[+-]Nunit} where @samp{+} or @samp{-} is the
sign, @samp{N} a number, and @samp{unit} the unit as discussed below.

Units:
@verbatim
  s  seconds
  m  minutes
  h  hours
  rs real-life seconds, as in including leap second transitions

  d  days
  b  business days
  mo months
  y  years
@end verbatim
