Invalid identifier error when all listed elements exist

I'm doing a basic database assignment on ETL. I'm trying to update a column by referencing three distinct columns in two other tables.

I am getting this error report in SQL Developer:

SQL Error: ORA-00904: "DIMTIME"."DAY_TIME": invalid identifier
00904. 00000 -  "%s: invalid identifier"` 

I feel my syntax is bad as all listed elements exist.

Code snippet is:

update fact_stage set date_sk = (
  select date_sk from time_stage
  where (time_stage.year_time = dimtime.year_time)
  and (time_stage.month_time = dimtime.month_time)
  and (time_stage.day_time = dimtime.day_time)
);