"boot time plus random offset" is going to be just as much of a fingerprint as "boot time" is, though (the offset can't change once picked for a boot because th

"boot time plus random offset" is going to be just as much of a fingerprint as "boot time" is, though (the offset can't change once picked for a boot because the whole point is to be able to calculate the time between events in the app). Something that reduces the granularity a lot, like "time since UTC 00:00:00 on the day of the last device boot", might work.