date/times must always be stored in UTC in the DB, then they can be converted to whatever timezone the user wants.
Then the dates can be shown in the specified user's local timezone or in UTC if the user didn't specify a timezone or the local time (OACS system timezone setting) if the site is a one timezone only site.
So you don't need 'lc_time_system_to_user' and 'lc_time_user_to_system' because date/times must the in UTC in the DB