Determine Week Start Date From Year And Number

Originally Posted by SalientAnimal

I just wanted to clarify what you meant by on 29 December. Does this mean is I use your tweak, that week one will start from 29 December of the previous year, provided 29 December is a Monday?

Would this also be true if the Monday is on 30 / 31 December of the previous year?

Yes - with ISO week numbers week 1 always starts with the Monday in the period 29 Dec - 4 Jan. How is week 1 defined in your system?

I doubt if WEEKNUM()-1 will get the correct week number in all years, it may work this year but for some years it probably tallies with WEEKNUM