Returns the span of time from @var{date1} to @var{date2} in terms of
@var{unit}, which must be a quoted string, one of @samp{years},
@samp{quarters}, @samp{months}, @samp{weeks}, @samp{days},
Returns the span of time from @var{date1} to @var{date2} in terms of
@var{unit}, which must be a quoted string, one of @samp{years},
@samp{quarters}, @samp{months}, @samp{weeks}, @samp{days},