I have an issue to make an application using Firebase analytics compliant with the GDPR (european law regarding data privacy). The GDPR requires the analytics data with implicit consent to be removed after 13 months. Firebase Analytics holds data for 14 months and then only keeps aggregated API.
I saw that it was possible to reduce this to 2 months, but that is too short for my usage. Is it possible to set it to 13 months, or to "manually" remove old sessions using BigQuery?
Data retention for Firebase Property can be set at 2 or 14 months: https://support.google.com/analytics/answer/7667196?hl=en
In any case, the retention of data is not correct to say that it must be 13 months, otherwise for web properties you could not choose 50 months before the expiration or that it never expires.
It is up to the data owner to define the data retention time justifying the use he makes of that data, based on his business, informing the user.
From BigQuery you cannot interact with Google Analytics server data, it is an export. They are two different systems, and BigQuery does not have the same restrictions as Google Analytics, so if you have to remove any data from there, you will have to do it by hand.