Fix time zone issue when calculating systemStart

Author: cffls

pycardano/backend/ogmios.py

@@ -1,3 +1,4 @@
+import calendar
 import json
 import time
 from typing import List, Union
@@ -109,10 +110,10 @@ def genesis_param(self) -> GenesisParameters:
         if not self._genesis_param or self._check_chain_tip_and_update():
             result = self._request(method, args)
             system_start_unix = int(
-                time.mktime(
+                calendar.timegm(
                     time.strptime(
                         result["systemStart"].split(".")[0], "%Y-%m-%dT%H:%M:%S"
-                    )
+                    ),
                 )
             )
             self._genesis_param = GenesisParameters(

test/pycardano/backend/test_ogmios.py

@@ -132,7 +132,7 @@ def test_genesis(self):
                 max_lovelace_supply=1000000000000,
                 network_magic=42,
                 epoch_length=500,
-                system_start=1640085434,
+                system_start=1640056634,
                 slots_per_kes_period=129600,
                 slot_length=1,
                 max_kes_evolutions=60000000,