I have Account - Opty as master- details, and I want one field at account object to capture sum of all related optys but only for those are in current fiscal year.
2 answers
Andrew Russo (BACA Systems) 
Forum Ambassador
i think you would need to use DLRS and have it run scheduled. because if it is a normal rollup that only runs on edit of the child opp then if there are no opps changed in 6 months the value on the account would be stale since it wouldn't have recalculated.
You can read the below documentation on DLRS. This is a really powerful tool that is managed by the salesforce.org team
https://www.salesforceben.com/guide-to-salesforce-dlrs-declarative-lookup-roll-up-summaries/
Installation Link:
