code: def _calc_julian_from_U_or_W(
      year, week_of_year, day_of_week, week_starts_Mon
  ):
      """Calculate the Julian day based on the year, week of the year, and day of
      the week, with week_start_day representing whether the week of the year
      assumes the week starts on Sunday or Monday (6 or 0)."""
      first_weekday = datetime_date(year, 1, 1).weekday()
      # If we are dealing with the %U directive (week starts on Sunday), it's
      # easier to just shift the view to Sunday being the first day of the
      # week.
      if not week_starts_Mon:
          first_weekday = (first_weekday + 1) % 7
          day_of_week = (day_of_week + 1) % 7
      # Need to watch out for a week 0 (when the first day of the year is not
      # the same as that specified by %U or %W).
      week_0_length = (7 - first_weekday) % 7
      if week_of_year == 0:
          return 1 + day_of_week - first_weekday
      else:
          days_to_week = week_0_length + (7 * (week_of_year - 1))
          return 1 + days_to_week + day_of_week
  
imports: import time
  import locale
  import calendar
  from re import compile
  from re import IGNORECASE
  from re import escape
  from datetime import date, timedelta, timezone
  from _thread import allocate_lock
label_desc: Use image node_id 2 for calling a global function with example usage: _calc_julian_from_U_or_W(year, week_of_year, day_of_week, week_starts_Mon) and returns: unknown, unknown