Calendar calculations - Printable Version +- HP Forums (https://www.hpmuseum.org/forum) +-- Forum: HP Calculators (and very old HP Computers) (/forum-3.html) +--- Forum: HP Prime (/forum-5.html) +--- Thread: Calendar calculations (/thread-3296.html) Calendar calculations - ggauny@live.fr - 03-07-2015 08:08 PM Good evening, Sometimes it is important to know in which number-week is a date of appointement, or a delivery post, a RDV for work and so on. I have maked this formula, according with ISO 8601 norm : N°week=IP([DOW(1/1/AAAA)+DOY(JJ,MMAAAA)+5]/7)-[IP(DOW(1/1/AAAA)/5] For example : in what week is 18/06/1582 ? N°W= DOW(1/1/1582) it is 1 DOY(18/06/1582) it is 169 then : 1+169+5 it is 175, then quotient by 7 it is 25 And because ip(1/5) it is 0 the anser is 25+0=25. well : the 18/06/1582 is into the week number 25. Gérard.(I dedicace for Katie because her is gentile). RE: Calendar calculations - Katie Wasserman - 03-12-2015 02:16 PM Gérard, I moved this to the Prime Forum for better visibility, and thank you for the dedication!