diff --git a/Dockerfile b/Dockerfile
index cf10bf4..e353c40 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,6 +1,9 @@
 FROM debian:bookworm-slim
 
-RUN groupadd --system --gid 10001 netfishing \
+RUN DEBIAN_FRONTEND=noninteractive apt-get update \
+	&& DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends tzdata \
+	&& rm -rf /var/lib/apt/lists/* \
+	&& groupadd --system --gid 10001 netfishing \
 	&& useradd --system --uid 10001 --gid netfishing \
 		--home-dir /var/lib/netfishing-server netfishing \
 	&& install -d -o netfishing -g netfishing \
diff --git a/README.md b/README.md
index 3f2d0ea..6abaaba 100644
--- a/README.md
+++ b/README.md
@@ -61,7 +61,11 @@ sudo ./scripts/rollback-native.sh
 ```
 
 Copy `config/server.cfg.example` to `/etc/netfishing-server.cfg` and adjust the
-room name, UDP port, player limit, and public-listing preference. Forward the
+room name, UDP port, player limit, and public-listing preference. Set `TZ` in
+`/etc/netfishing-server.env` to an IANA timezone such as `America/New_York` when
+the server's world should follow that region's wall clock and daylight-saving
+rules; the packaged default is `UTC`. The timezone must be present before the
+server process starts, so restart the service after changing it. Forward the
 configured UDP port through the host firewall and router when accepting
 Internet players.
 
@@ -135,8 +139,8 @@ docker compose up -d
 ```
 
 Set values such as `NETFISHING_SERVER_NAME`, `NETFISHING_SERVER_PORT`,
-`NETFISHING_SERVER_MAX_PLAYERS`, `NETFISHING_SERVER_PUBLIC`, and the optional
-comma-separated `NETFISHING_SERVER_OPERATORS` in a local `.env` file. The
+`NETFISHING_SERVER_MAX_PLAYERS`, `NETFISHING_SERVER_PUBLIC`, `TZ`, and the
+optional comma-separated `NETFISHING_SERVER_OPERATORS` in a local `.env` file. The
 Compose service runs without Linux capabilities, uses a read-only root
 filesystem, and stores persistent state in a named volume.
 
diff --git a/compose.yaml b/compose.yaml
index 413342c..50a8fcd 100644
--- a/compose.yaml
+++ b/compose.yaml
@@ -18,6 +18,7 @@ services:
       NETFISHING_SERVER_PUBLIC: "${NETFISHING_SERVER_PUBLIC:-false}"
       NETFISHING_DISCOVERY_URL: "${NETFISHING_DISCOVERY_URL:-https://discovery.netfishing.org}"
       NETFISHING_DATA_DIR: /var/lib/netfishing-server
+      TZ: "${TZ:-UTC}"
       NETFISHING_SERVER_OPERATORS: "${NETFISHING_SERVER_OPERATORS:-}"
     volumes:
       - netfishing-server-data:/var/lib/netfishing-server
diff --git a/config/netfishing-server.env.example b/config/netfishing-server.env.example
index 78d7c16..dbabf24 100644
--- a/config/netfishing-server.env.example
+++ b/config/netfishing-server.env.example
@@ -5,4 +5,5 @@ NETFISHING_SERVER_MAX_PLAYERS=8
 NETFISHING_SERVER_PUBLIC=false
 NETFISHING_DISCOVERY_URL=https://discovery.netfishing.org
 NETFISHING_DATA_DIR=/var/lib/netfishing-server
+TZ=UTC
 NETFISHING_SERVER_OPERATORS=
diff --git a/systemd/netfishing-server.service b/systemd/netfishing-server.service
index 3cae181..7e936a0 100644
--- a/systemd/netfishing-server.service
+++ b/systemd/netfishing-server.service
@@ -8,6 +8,7 @@ Type=simple
 User=netfishing
 Group=netfishing
 WorkingDirectory=/opt/netfishing-server/current
+Environment=TZ=UTC
 EnvironmentFile=-/etc/netfishing-server.env
 ExecStart=/opt/netfishing-server/current/NETfishingServer.x86_64 -- --config=/etc/netfishing-server.cfg
 Restart=on-failure