diff --git a/lib/space_lua/stdlib/os.ts b/lib/space_lua/stdlib/os.ts
index 3279ef2b..1b2ddc76 100644
--- a/lib/space_lua/stdlib/os.ts
+++ b/lib/space_lua/stdlib/os.ts
@@ -136,7 +136,7 @@ export const osApi = new LuaTable({
       // Day of the week
       "%A": () => date.toLocaleString("en-US", { weekday: "long" }),
       "%a": () => date.toLocaleString("en-US", { weekday: "short" }),
-      "%w": () => "" + (date.getDay() + 1),
+      "%w": () => "" + date.getDay(),
       // Day of the year
       "%j": () => {
         return dayOfYear(date).toString().padStart(3, "0");
diff --git a/lib/space_lua/stdlib/os_test.lua b/lib/space_lua/stdlib/os_test.lua
index 6f8b0652..8fee0d64 100644
--- a/lib/space_lua/stdlib/os_test.lua
+++ b/lib/space_lua/stdlib/os_test.lua
@@ -20,3 +20,5 @@ assert(os.date("%U %V %W", os.time({ year = 2025, month = 1, day = 5 })) == "01
 assert(os.date("%U %V %W", os.time({ year = 2025, month = 1, day = 6 })) == "01 02 01")
 assert(os.date("%U %V %W", os.time({ year = 2025, month = 1, day = 7 })) == "01 02 01")
 assert(os.date("%U %V %W", os.time({ year = 2025, month = 5, day = 3 })) == "17 18 17")
+
+assert(os.date("%w", 1750672800) == "1")