bool_in bool_out pg_date_in pg_date_out pg_interval_cmp pg_interval_in pg_interval_make pg_interval_mul pg_interval_out pg_interval_pl pg_time_in pg_time_out pg_timestamp_in pg_timestamp_mi pg_timestamp_mi_interval pg_timestamp_out pg_timestamp_pl_interval pg_timestamptz_in pg_timestamptz_out

pg_timestamp_pl_interval() TimestampTz pg_timestamp_pl_interval ( TimestampTz  timestamp, const Interval *  span  ) Add an interval to a timestamp data type. Note that interval has provisions for qualitative year/month and day units, so try to do the right thing with them. To add a month, increment the month, and use the same day of month. Then, if the next month has fewer days, set the day of month to the last day of month. To add a day, increment the mday, and use the same time of day. Lastly, add in the "quantitative time". Note PostgreSQL function: Datum timestamp_pl_interval(PG_FUNCTION_ARGS)