FAQ.md

README.md

@@ -176,6 +176,7 @@ Successful tested with:
 - Ubuntu 22.10 (Kinetic Kudu)
 
 Not working with:
+
 - Debian 11 (Bullseye) and lower (missing `python-jose` dependency)
 - Ubuntu 22.04 (Jammy Jellyfish) (not supported as for 15.01.2023 due to [fastapi - uvicorn version missmatch](https://bugs.launchpad.net/ubuntu/+source/fastapi/+bug/1970557))
 
@@ -249,6 +250,16 @@ After first success you have to replace `--issue` with `--renew`.
 every 4.8 hours. If network connectivity is lost, the loss of connectivity is detected during license renewal and the
 client has 19.2 hours in which to re-establish connectivity before its license expires.
 
+```python
+from datetime import timedelta
+
+LEASE_RENEWAL_PERIOD=0.2  # 20%
+delta = timedelta(days=1)
+renew = delta.total_seconds() * LEASE_RENEWAL_PERIOD
+renew = timedelta(seconds=renew)
+expires = delta - renew  # 19.2
+```
+
 \*2 Always use `https`, since guest-drivers only support secure connections!
 
 \*3 If you recreate instance keys you need to **recreate client-token for each guest**!