-double expr_ymd_to_date (double year, double month, double day);
-double expr_ymd_to_ofs (double year, double month, double day);
-double expr_wkyr_to_date (double wk, double yr);
-double expr_yrday_to_date (double yr, double day);
-double expr_yrmoda (double year, double month, double day);
+double expr_ymd_to_date (int year, int month, int day,
+ const struct expression *, const struct expr_node *,
+ int ya, int ma, int da);
+double expr_ymd_to_ofs (int y, int m, int d,
+ const struct expression *, const struct expr_node *,
+ int ya, int ma, int da);
+double expr_date_difference (double date1, double date2,
+ struct substring unit, const struct expression *,
+ const struct expr_node *);
+double expr_date_sum (double date, double quantity, struct substring unit_name,
+ struct substring method_name,
+ const struct expression *, const struct expr_node *);
+double expr_date_sum_closest (double date, double quantity,
+ struct substring unit_name,
+ const struct expression *,
+ const struct expr_node *);