diff --git a/spec/unit/features/cost_budget.feature b/spec/unit/features/cost_budget.feature
index 50c66a6..c63bfb2 100644
--- a/spec/unit/features/cost_budget.feature
+++ b/spec/unit/features/cost_budget.feature
@@ -117,7 +117,7 @@ Feature: Cost budget limiter module behavior
 
     Scenario: computes weekly period boundary aligned to Monday UTC
       When I compute period start for period "7d" at now 1770129000
-      Then the period start is 1769904000
+      Then the period start is 1769990400
 
     Scenario: rejects unknown period in period start computation
       When I compute period start for period "30m" at now 1770129000
diff --git a/src/fairvisor/cost_budget.lua b/src/fairvisor/cost_budget.lua
index fc85f26..570f5d4 100644
--- a/src/fairvisor/cost_budget.lua
+++ b/src/fairvisor/cost_budget.lua
@@ -92,7 +92,7 @@ function _M.compute_period_start(period, now)
   end
 
   if period == "7d" then
-    return floor((now - 259200) / 604800) * 604800 + 259200
+    return floor((now - 345600) / 604800) * 604800 + 345600
   end
 
   return nil, "unknown period"