diff --git a/cardano-testnet/changelog.d/20260226_005016_palas_default_to_update_timestamps.md b/cardano-testnet/changelog.d/20260226_005016_palas_default_to_update_timestamps.md
new file mode 100644
index 00000000000..601ffd92964
--- /dev/null
+++ b/cardano-testnet/changelog.d/20260226_005016_palas_default_to_update_timestamps.md
@@ -0,0 +1,8 @@
+### Added
+
+- Added `--no-update-time` flag.
+
+### Changed
+
+- Made `--update-time` flag the default.
+
diff --git a/cardano-testnet/src/Parsers/Cardano.hs b/cardano-testnet/src/Parsers/Cardano.hs
index d6797eb1ac4..fef2171a6d8 100644
--- a/cardano-testnet/src/Parsers/Cardano.hs
+++ b/cardano-testnet/src/Parsers/Cardano.hs
@@ -132,11 +132,14 @@ pMainnetParams = OA.flag' OnChainParamsMainnet
   )
 
 pUpdateTimestamps :: Parser UpdateTimestamps
-pUpdateTimestamps = OA.flag DontUpdateTimestamps UpdateTimestamps
-  (  OA.long "update-time"
-  <> OA.help "Update the time stamps in genesis files to current date"
-  <> OA.showDefault
-  )
+pUpdateTimestamps =
+  -- Default to UpdateTimestamps, because when using the two-step flow
+  -- (cardano-testnet create-env → cardano-testnet cardano --node-env),
+  -- genesis timestamps can become stale.
+  -- See https://github.com/IntersectMBO/cardano-node/issues/6455
+  OA.flag' UpdateTimestamps (OA.long "update-time" <> OA.help "Update the time stamps in genesis files to current date (default, kept for backward compatibility)")
+  <|> OA.flag' DontUpdateTimestamps (OA.long "no-update-time" <> OA.help "Do not update the time stamps in genesis files to current date.")
+  <|> pure UpdateTimestamps
 
 pEnvOutputDir :: Parser FilePath
 pEnvOutputDir = OA.strOption
diff --git a/cardano-testnet/test/cardano-testnet-golden/files/golden/help.cli b/cardano-testnet/test/cardano-testnet-golden/files/golden/help.cli
index d3921a1cf8d..bac8219efac 100644
--- a/cardano-testnet/test/cardano-testnet-golden/files/golden/help.cli
+++ b/cardano-testnet/test/cardano-testnet-golden/files/golden/help.cli
@@ -12,7 +12,7 @@ Usage: cardano-testnet cardano [--num-pool-nodes COUNT]
   [--slot-length SECONDS]
   [--active-slots-coeff DOUBLE]
   [--node-env FILEPATH]
-  [--update-time]
+  [--update-time | --no-update-time]
 
   Start a testnet and keep it running until stopped
 
diff --git a/cardano-testnet/test/cardano-testnet-golden/files/golden/help/cardano.cli b/cardano-testnet/test/cardano-testnet-golden/files/golden/help/cardano.cli
index cc26e43d032..098999aa11c 100644
--- a/cardano-testnet/test/cardano-testnet-golden/files/golden/help/cardano.cli
+++ b/cardano-testnet/test/cardano-testnet-golden/files/golden/help/cardano.cli
@@ -10,7 +10,7 @@ Usage: cardano-testnet cardano [--num-pool-nodes COUNT]
   [--slot-length SECONDS]
   [--active-slots-coeff DOUBLE]
   [--node-env FILEPATH]
-  [--update-time]
+  [--update-time | --no-update-time]
 
   Start a testnet and keep it running until stopped
 
@@ -51,5 +51,7 @@ Available options:
                            with the 'create-env' command, then modify it and
                            pass it with this argument.
   --update-time            Update the time stamps in genesis files to current
-                           date
+                           date (default, kept for backward compatibility)
+  --no-update-time         Do not update the time stamps in genesis files to
+                           current date.
   -h,--help                Show this help text