diff --git a/backend/db/db.go b/backend/db/db.go
index 315118a..366b374 100644
--- a/backend/db/db.go
+++ b/backend/db/db.go
@@ -23,7 +23,12 @@ func Connect() error {
 		getEnv("POSTGRES_DB"),
 	)
 
-	pool, err := pgxpool.New(context.Background(), dsn)
+	poolCfg, err := pgxpool.ParseConfig(dsn)
+	if err != nil {
+		return err
+	}
+	poolCfg.ConnConfig.RuntimeParams["timezone"] = "UTC"
+	pool, err := pgxpool.NewWithConfig(context.Background(), poolCfg)
 	if err != nil {
 		return err
 	}
diff --git a/backend/db/db_dev.go b/backend/db/db_dev.go
index 3724cf0..ffca459 100644
--- a/backend/db/db_dev.go
+++ b/backend/db/db_dev.go
@@ -22,7 +22,12 @@ func Connect() error {
 		getEnv("POSTGRES_DB"),
 	)
 
-	pool, err := pgxpool.New(context.Background(), dsn)
+	poolCfg, err := pgxpool.ParseConfig(dsn)
+	if err != nil {
+		return err
+	}
+	poolCfg.ConnConfig.RuntimeParams["timezone"] = "UTC"
+	pool, err := pgxpool.NewWithConfig(context.Background(), poolCfg)
 	if err != nil {
 		return err
 	}
diff --git a/backend/db/proxy.go b/backend/db/proxy.go
index 82863c1..8a30fa6 100644
--- a/backend/db/proxy.go
+++ b/backend/db/proxy.go
@@ -11,6 +11,20 @@ import (
 // Querier is implemented by *pgxpool.Pool, pgx.Tx, and *PoolProxy.
 // Fixture functions and internal helpers that need to run queries should
 // accept Querier to remain decoupled from transaction state.
+//
+// DISTINCTION: QueryRow vs Querier
+// - QueryRow() (lowercase 'r') is a METHOD on Querier. It returns pgx.Row.
+//   Call it like: row := q.QueryRow(ctx, sql, args...)
+// - Querier (uppercase 'Q') is an INTERFACE. It declares the QueryRow method.
+//   Accept Querier when a helper must work with both pool + transactions.
+// - pgx.Row (singular) is the RETURN TYPE of QueryRow(). It is NOT a Querier.
+//   pgx.Row only has Scan(). You cannot pass a pgx.Row where Querier is expected.
+//
+// Common mistake:
+//   // WRONG — pgx.Row does not implement Querier:
+//   func helper(ctx, row pgx.Row) { ... }
+//   // CORRECT — accept Querier, call QueryRow inside:
+//   func helper(ctx, q db.Querier) { row := q.QueryRow(ctx, sql, args...); ... }
 type Querier interface {
 	Exec(ctx context.Context, sql string, args ...any) (pgconn.CommandTag, error)
 	Query(ctx context.Context, sql string, args ...any) (pgx.Rows, error)