In Sybase Adaptive Server Enterprise (ASE) you can use DAY function to get the day (an integer number) of the specified datetime. In Oracle you have to use EXTRACT(DAY FROM datetime) function.
Sybase ASE:
-- Get the day SELECT DAY('2022-12-28'); # 28
Oracle:
-- Get the day SELECT EXTRACT(DAY FROM DATE '2022-12-28'); # 28
For more information, see Sybase ASE to Oracle Migration.