Following session variables (similar to tsf_appl_lang_id) will help to make good performing queries that contain UTC to Local time conversion
tsf_appl_time_zone
returns the end user time zone as is saved in IAM
tsf_appl_time_zone_sql
returns the end user time zone as is saved in IAM, converted to the time zone id in SQL Server
tsf_appl_utc_offset
returns the offset in minutes, between UTC and time zone that is set by the end user
See also here:
