diff --git a/src/lune/builtins/datetime/builder.rs b/src/lune/builtins/datetime/builder.rs
index 7b2c4b8..8ede807 100644
--- a/src/lune/builtins/datetime/builder.rs
+++ b/src/lune/builtins/datetime/builder.rs
@@ -98,7 +98,7 @@ impl DateTimeBuilder {
     {
         let format = match format {
             Some(fmt) => fmt.to_string(),
-            None => "%Y-%m-%dT%H:%M:%SZUTC+%z".to_string(),
+            None => "%Y-%m-%dT%H:%M:%SZ".to_string(),
         };
 
         let locale = match locale {
diff --git a/src/lune/builtins/datetime/mod.rs b/src/lune/builtins/datetime/mod.rs
index 4b4391e..1409771 100644
--- a/src/lune/builtins/datetime/mod.rs
+++ b/src/lune/builtins/datetime/mod.rs
@@ -153,7 +153,7 @@ impl<'lua> FromLua<'lua> for DateTimeBuilder {
                 .with_hour(t.get("hour")?)
                 .with_minute(t.get("minute")?)
                 .with_second(t.get("second")?)
-                .with_millisecond(t.get("millisecond")?)
+                .with_millisecond(t.get("millisecond").or(LuaResult::Ok(0))?)
                 .build()),
             _ => Err(LuaError::external(
                 "expected type table for DateTimeBuilder",