Reversed weeknumber function?

[Jaymond Flurrie]

I have like this:
Source Date: December 31st, 2020
Result: 53/2020
Formula: WEEKNUM(A1;21)&"/"&YEAR(A1)

But how about the same backwards, what would you suggest? The exact date would preferably be the particular Monday.

So input: 53/2020 (which can be parsed obviously to 53 and 2020 with a split at the slash)
should somehow calculate 44193 (which is December 28th 2020).

I was thinking of making simply a large lookup table, but I have a feeling that's unnecessary.

Oh and I need to do this without VBA, just by using Excel functions.

 

[Tetra201]

Kudos to @ felixstraube for discovering a glitch in my formula from Post #29 -- it returns "53/1954" for 28-Dec-1953, which is obviously incorrect.

However, the formula suggested by felixstraube in Post #30, has a glitch as well -- it returns "53/1954" for 1-Jan-1954, which is also incorrect.

Here is an extensively tested formula (years 1950 through 2130) that seems to have no glitches:

=WEEKNUM(A1,21)&"/"&YEAR(WORKDAY.INTL(A1-4,1,"1110111"))

 

[felixstraube]

You nailed it!

I tested it with the 7 first and the 7 last days of every year from 1901 to 2200 and it always gave the expected result.