Change cell format code to display ISO-8601 week number for WW

I use one sheet in Calc to track writing progress daily and use week numbers to coordinate that sheet with a week-based sheet (and some other programs) using the ISO-8601 dating format.

The date column’s cells, I have the Date “cell format code” set to:


So that when I type in 1/1/2021 (or a similar date), it displays:
Fri, 01/01/2021 (1)

With the calendar week number being in parenthesis.

This worked like gangbusters in years past. But the end of 2020, by ISO-8601 standards, had a “leap week”. So I’d like it to display Fri, 01/01/2021 (53). (My other two programs were consistent with this number; LO was the only odd one out.)

I don’t want to make another column with a formula to calculate WEEKNUM (as it shown in )–I just figure there’s some option I’m overlooking that will switch on this “week 53” for WW.


Cell format code
NN, MM/DD/YYYY" (“WW”)" for date 01/01/2021 to produce: Fri, 01/01/2021 (53)

actual output:
NN, MM/DD/YYYY" (“WW”)" for date 01/01/2021 currently produces: Fri, 01/01/2021 (01)

How can I change what that “WW” displays, without using a formula?

Thank you for your time and help!