how calculate date from year, week number and weekday?

You might have to settle for an approximation. This is what I tried...

let myYear := 2019;
let myMonth := 0;
let myWeek := 14;
let myDay := 0;
myMonth := floor(myWeek / 4);
myDay := myWeek % 4 * 7;
let myDate := date(myYear, myMonth, myDay);

or

myDate := date(myYear, floor(myWeek / 4), myWeek % 4 * 7)

agiorno, you're welcome. If you consider 4/1/2019 (d/m/y) to be the first odd Friday, then you could use...

date(year, month, day + multiples of 14) 

to get the correct dates. I don't know if you want the dates all at once or as you need them. You could use a loop to get them all at once. As for using Day names instead of numbers, use the format() function. You can find the various format options here...

https://ninoxdb.de/en/manual/calculations/reference-of-functions-and-language

Well, I just figured out the multiples of 14 will increment the weeks, but it doesn’t help with returning only the odd weeks. It will be later today before I can look at it again.

@Agiorno

The function

week('Booking Date') 

Will give you the week of the year.. I will have to dig through my notes.. There is a function that gives you the remainder.. So you can divide the week by 2 .. If there is a remainder.. it is ODD.. else even.. 

I'm close.. just need that last step.. :) 

@Agiorno...   Here ya go..  The ever elusive modulo function.. :) 

https://ninoxdb.de/en/forum/ideas-and-suggestions-5abb9f4f45eda7ea1e75ed02/suggest-include-modulo-function-in-documentation-5b05142a54369026ffa70518?post=5b05142a54369026ffa70519&page=0

So.. 

let mod := week('Booking Date') % 2;

if mod = 0 then  
    .... week is even ... 
else
   .... week is odd ....   

@Mconneen, Looks like I'm forever reinventing the wheel! That solves the odd/even as far as the calendar goes, but still leaves the requirement of constraining the schedule. Not enough information for me to say how.

While not a reply to help, I need a list of the first Mondays of each week between two dates.

kgb

This block of code might seem a little awkward but it works and you can write it as function: my_function(year, week, week_day), keep it in the Options Panel - Global Script Definitions, and call the function from anywhere in the DB.

let year := 2020;
let week := 37;
let day:= 4;

let yDate := (date(year,1,1));                                "Date of the 1st day of the year as a date data type";
let yEpoch := number(date(year,1,1));                   "same as a number - Epoch date";
let wDay := weekday(yDate);                                "week day of the 1st day of the year as a number";
let LydEpoch := wDay * 24 * 60 * 60 * 1000;         "Last year days in the first week - Epoch time lapse";
let wEpoch := (week-1) * 7 * 24 * 60 * 60 * 1000; "weeks in the current year - Epoch time lapse";
let dEpoch := day * 24 * 60* 60 * 1000;                "days in the last week - Epoch time lapse";
date(yEpoch - LydEpoch + wEpoch + dEpoch);

In this case you get

11 Sep 2020

Which is the correct date.

You can try with other vakues for year, week, day using the Console.

To calculate the date for each friday in whatever year you could use a loop and call the function:

let year := 2019;
let day:= 4;
for week in range(1,54) do
    let my_day := my_function(year, week, day);
    /* Since in a year you may have 366/7 = 52,28 weeks you have to loop */
    /* through 53 weeks and test my_day to see if it is after the last day in the year */
end

As for the list of Mondays between two dates the above function could be used within the same year, having day := 0 and looping through week numbers in the data range.