How do you model working capital where the lag is more than the model frequency?

Working Capital Model can be done on the basis of 2 things i.e Current Asset except Cash and Current Liabilities except Short Term Debt. Accounts Receivable, Inventory Turnover and Accounts Payables can be calculated on the basis of AR,Inv & AP days. 

It might happen that the payable days are more than the receivables then in that case Working Capital will be negative and more accurate analysis can be drawn through Cash Conversion Cycle i.e AR days+Inventory Days- Payable Days. It shows how long does it take for a firm to convert sales to cash