You can't change them for the 24 open periods you are in once you have set them up. However, when you close the year (year end wizard) you can enter the new periods into the 13-24 periods and set them to be quarterly. Be aware if you run financial statement comparison reports for last year compared to the current year after you close the 1st year of period 1-12, the report will not give you an accurate comparison because last year will be over 1 month for period 1 and the current year will report for 3 months in period 13. If you need the fiscal periods to be quarterly in the 24 open periods you have now, we can fix your data to reflect this. Their is a charge for our service. We can fix this for you in 1 day. Please call if you are interested in our service.