= expr_date_difference (date1, date2, unit);
no_abbrev function DATESUM (date, quantity, string unit)
= expr_date_sum (date, quantity, unit, ss_cstr ("closest"));
= expr_date_difference (date1, date2, unit);
no_abbrev function DATESUM (date, quantity, string unit)
= expr_date_sum (date, quantity, unit, ss_cstr ("closest"));