Right now tasks can be set to repeat over up to 12 weeks:
If you add one more value to that dropdown (13) you’ll be able to support teams that follow the 4-4-5 calendar.
In this calendar, the year is divided into 4 perfect quarters of 13 weeks each.
Teams who adopt this calendar want to schedule quarterly activities (such as OKR setting and scoring) to recur every 13 weeks.
Hi @Vero_Rebagliatte, thanks for reaching out and sharing your feedback with us! As it stands, it’s currently not possible to select 13 weeks. We don’t have immediate plans to implement this feature but I’ll keep you posted once I have any news!
I am looking to set a 13 week recurring task - it needs to be 13 weeks to match a quarter. The 3 month recurring does not work as it recurs on the same date of the month.
EG - 1st task dated 1st June. Next task should be 31st Aug on 13 week recurring, but with 3 month recurring this would generate a new task for 1st Sept.
Does anyone have any advice? 
Hi @Emma_McCrindle, welcome to the Asana Community Forum!
It’s currently not possible to select one specific day every three months, you can set your task to repeat every 3 months on the last day of the month:
Let’s see what the other community members do in this type of cases 
