Apache Druid segment granuality

In Apache Druid configuration you can select the granuality of the segments (hour/day/week/etc.). What will happen if you change the granuality later? Will the new settings be applied just to the new data and old segments will be left as it is, or it will regenerated old segments too? for example, if we decide to change from day granuality to week..

This is a companion discussion topic for the original entry at https://stackoverflow.com/questions/74015437/apache-druid-segment-granuality