@Rachel , the elements in a calendar identifier will be of equal length - the unit you specify in the declaration.



May I ask what is the need to implement a 4-4-5... calendar ?



One way for you to do this is to declare a calendar with week (7 * day) as the unit, you will get a calendar of weeks.



Now, create a separate set, say TimePeriods with elements Period-1, Period-2, ..... Now you can map the weeks to these periods, Period-1 contains weeks 1 to 4, Period-2 is weeks 5 to 8 and Period-3 is weeks 9 to 13 and so on.

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Thanks Mohan. Rather than the calendar, I meant the periods within the horizon and this solution would do it. Currently we are investigating demand systems where demand data is in monthly buckets, but our production planning is done weekly. In implementations I've done with other products, using a 4-4-5 methodology is helpful to get users heads around what is happening as the first day of a period is always a Monday (for example) even if the months don't line up exactly.

Thanks for your help

Rachel

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