https://community.appian.com/discussions/f/rules/6434/hi-i-have-a-problem-with-the-rule-weeknum-evaluated-oHi, I have a problem with the rule &quot;weeknum()&quot;: evaluated on Monday 4th of January 2016 it returns the week number 2 when outlook (following to my knowledge the norm ISO-8601) indicates 1 for this week. Hence there is a shift for all of the followingen-USTelligent Community 12https://community.appian.com/thread/81481?ContentTypeID=1Mon, 10 May 2021 07:02:53 GMTd3a83456-d57b-489c-a84c-4e8267bb592a:770bb3a0-d49f-4027-ac59-6e2e12317782sindhug0003<p>Thanks, This logic helped us !!</p><div style="clear:both;"></div>https://community.appian.com/thread/45494?ContentTypeID=1Wed, 17 May 2017 13:26:59 GMTd3a83456-d57b-489c-a84c-4e8267bb592a:08eb42e5-abc6-4df7-b940-01cd991e00c0Sandro OberdorferThanks, we just ran into that issue and this really helped!<div style="clear:both;"></div>https://community.appian.com/thread/25257?ContentTypeID=1Mon, 07 Dec 2015 17:47:31 GMTd3a83456-d57b-489c-a84c-4e8267bb592a:65d90f46-9895-4185-9dc0-acd938a672cbVictor BoucherylastWeek:<br />if(<br /> contains(<br /> /* 53rd week year */<br /> {<br /> 2009,<br /> 2015,<br /> 2020,<br /> 2026,<br /> 2032<br /> },<br /> ri!year<br /> ),<br /> 53,<br /> 52<br />)<div style="clear:both;"></div>https://community.appian.com/thread/25256?ContentTypeID=1Mon, 07 Dec 2015 17:46:19 GMTd3a83456-d57b-489c-a84c-4e8267bb592a:a56bd801-1fb0-44da-82bf-e45297b5f3f8Victor BoucheryHere is the implementation of the rule. <br />weeknumCustom: <br />with(<br /> local!weeknum: int(<br /> (<br /> dayofyear(<br /> ri!date<br /> ) - userweekday(<br /> ri!date,<br /> 2 /* monday to sunday */<br /> ) + 10<br /> ) / 7<br /> ),<br /> if(<br /> local!weeknum &lt; 1,<br /> rule!lastWeek(<br /> year(<br /> ri!date<br /> ) - 1<br /> ),<br /> if(<br /> local!weeknum &gt; rule!lastWeek(<br /> year(<br /> ri!date<br /> )<br /> ),<br /> 1,<br /> local!weeknum<br /> )<br /> )<br />)<div style="clear:both;"></div>https://community.appian.com/thread/25180?ContentTypeID=1Wed, 02 Dec 2015 21:33:07 GMTd3a83456-d57b-489c-a84c-4e8267bb592a:90600a99-7f36-4f24-aac1-56ba4486c454Victor BoucheryOk, I going to write a rule for that. <br />Thanks for the link.<div style="clear:both;"></div>https://community.appian.com/thread/25179?ContentTypeID=1Wed, 02 Dec 2015 20:42:17 GMTd3a83456-d57b-489c-a84c-4e8267bb592a:05e6c8f0-10f9-4532-82bc-7960e163271fLakshmi MeyyappanThis seems to be a limitation of Appian because it did not correctly take into account week 53 for 2015. You should be able to write the logic to calculate it yourself, you can find the formula online (<a href="https://en.wikipedia.org/wiki/ISO_week_date#Calculation)">en.wikipedia.org/.../ISO_week_date</a> and you can write an expression rule to perform this calculation with logic to check for a possible week 53.<div style="clear:both;"></div>