## Prior Year on Weekly Module

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## Prior Year on Weekly Module

Hi All, Thought I would post this question... I'm working on a model with a weekly timescale. (13 4Week periods) Normally there is 52 weeks in a year, but every few years there will be a 53rd week. I was planning to use a LAG() function to pull the PY value. Offset would work too.

`LAG( Source Line Item, 52 , 0 )`

I have to hard code 52 into the formula, so not sure what will happen in 53 week years. Any ever looked at this in the past. I am going to look into it today so will post a solution if I find one. Thanks, Simon

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Previous Contributor

## RE: Prior Year on Weekly Module

Hi Simon Could it be the solution - when you compare values using start date for target week? E.g. you calc on week timescale lineitem date was year ago = start()-365 then you use formula=source_lineitem[lookup: date was year ago]
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Previous Contributor

## RE: Prior Year on Weekly Module

Hi Simon, I've had similar issues when I have wanted to apply IF statements referring to when time = YTD/FY. The challenge is that it doesn't seem possible to refer to the time of an item. My solution was to set up a new line item as boolean, then check true / false depending on how I want the formula to treat it. I made all months = TRUE and all YTD/FY summaries = FALSE. For your example you could check TRUE for any periods that are 53 - then apply an if statement. Make sense?
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