YearWeek calculation

I think the transformer you need is the DateTimeCalculator.

You will need to embed that in a custom transformer to create a loop construction and loop until you reach the current week.

Or the python way: 

In a Python Creator and expose the attribute 'YearWeeks'

import fmeobjects
from datetime import datetime, timedelta


class FeatureCreator(object):
    def __init__(self):
        pass
    def close(self):
        startDateText = "201742" # put a start date of a week before needed
        today = datetime.now() 
        d = timedelta(weeks=1)
        endDateText = today.strftime("%Y%W")
        Currentdate = datetime.strptime("{}0".format(startDateText),"%Y%W%w")
        # had to add a weekday number to get a datetime value
        CurrentText = "0"
       
        while int(CurrentText) < int(endDateText):
            feature = fmeobjects.FMEFeature()
            Currentdate = Currentdate + d
            CurrentText =  Currentdate.strftime("%Y%W")
            feature.setAttribute("YearWeeks",CurrentText) 
            self.pyoutput(feature)

I don't like putting the week before in (201742) and also having numbers as text but datetime uses string as input and outputs. But it does work