What is it that the users are looking for? Are they trying to determine differences / similarities, missing data, specific data? And are they looking for differences in the WW or the YYYY?
@Benny suggested right aligning the dates, but I have to disagree with that. The example given is not easily scannable. Rows 4 and 6 carry (approx) the same visual weight, but they couldn't be further apart in value. Rows 4 and 5 are the same date, but row 5 is holding more visual weight due to its length. This works in spreadsheets for numerical values, because left-aligned values with enough zeros like 1 million and 10 million look pretty similar. It isn't until they are right aligned that we can easily visualize the numeric differences.
So, figure out the goal of the user and craft your grid to aid in that. Are they looking for dates without a WW value? Are they looking for dates that fall within a range? Determining the goal may answer the question of alignment and how many cols to use.