My budget model's calendar type is Month/Quarter/Years but I need to do some calculations by bi-weekly pay periods and then roll up the result (using SUM) to month. Our payroll calendar varies by year.
I created a Pay Period Lists and a management module to map the Pay Period to the Month and Year it belongs. Please see the attached file. I still need to work on not hard coding year etc., but I wanted to consult with our experts to make sure that my approach is not against Anaplan best practice.
Your approach looks okay to me if you have ruled out using the regular Time feature using Weeks and a time filter to show only pay periods.
Mapped alt-Time lists give us flexibility, but be aware that alt-Time lists don't automatically handle any of the conveniences (switchover date, current period, PREVIOUS, etc.) that are provided by the model calendar. Most of those features can be built with a bit of creativity and effort, The alternative is to use the stock time feature with the week level (4-4-5, 4-5-4 or 5-4-4) with weeks rolling up to months. To show only pay periods (even or odd weeks) you would use a time filter to suppress alternating weeks. You could use a Time Range configured at the Month level for other (non-payroll) modules.
If converting your model to weeks isn't an option, an alternative solution may be to create a separate model (weeks based) and import the # of weeks in a given month. For example, a 4-4-5 calendar would import 4 weeks to the first period of the quarter. This would result in the 3rd period having 2.5x pay to accommodate the extra week.