About timestamp begin - end in API get flights

Dear community,

I am complete newby here, but what I already saw and found out looks great (was able to connect to the Get State and Get Flights API).
But I am struggling with the timestamp, as it seems that in the GET /flights/all API it's only available with a time delay?

Setup:
- if I use for begin a timestamp now()-3600 and for end a timestamp now()-1200 I do not receive any values
- if I use the same function with begin a timestamp now()-500000 and for end a timestamp now()-498000 it works perfectly.
(note: 500.000 seconds are roughly 6 days)

Questions:
1.) How long can I go back to receive data?
2.) What's the minimum time distance I have to maintain to now() to receive data?

Thanks a lot (and sorry for asking, but in the opensky-network.org/apidoc/rest.html#id6 documentation was no hint about that)

Have a good evening,
Tobias

Flights are only calculated at night (UTC) for the previous day, so there's no set distance.

Is this the case for Flights by Aircraft api at /flights/aircraft as well?