diff --git a/compiler/erg_common/python_util.rs b/compiler/erg_common/python_util.rs
index 80659611..d7bae2c2 100644
--- a/compiler/erg_common/python_util.rs
+++ b/compiler/erg_common/python_util.rs
@@ -6,7 +6,8 @@ use std::process::Command;
 use crate::serialize::get_magic_num_from_bytes;
 
 #[cfg(unix)]
-pub const BUILTIN_PYTHON_MODS: [&str; 18] = [
+pub const BUILTIN_PYTHON_MODS: [&str; 19] = [
+    "datetime",
     "glob",
     "http",
     "importlib",
@@ -27,7 +28,8 @@ pub const BUILTIN_PYTHON_MODS: [&str; 18] = [
     "zipfile",
 ];
 #[cfg(not(unix))]
-pub const BUILTIN_PYTHON_MODS: [&str; 17] = [
+pub const BUILTIN_PYTHON_MODS: [&str; 18] = [
+    "datetime",
     "glob",
     "http",
     "importlib",
diff --git a/compiler/erg_compiler/context/initialize/mod.rs b/compiler/erg_compiler/context/initialize/mod.rs
index c6dc1467..22698bec 100644
--- a/compiler/erg_compiler/context/initialize/mod.rs
+++ b/compiler/erg_compiler/context/initialize/mod.rs
@@ -130,8 +130,13 @@ impl Context {
         }
     }
 
-    fn register_builtin_immutable_private_var(&mut self, name: &'static str, t: Type) {
-        self.register_builtin_impl(name, t, Immutable, Private);
+    fn register_builtin_immutable_private_var(
+        &mut self,
+        name: &'static str,
+        t: Type,
+        py_name: Option<&'static str>,
+    ) {
+        self.register_builtin_py_impl(name, t, Immutable, Private, py_name);
     }
 
     fn register_builtin_const(&mut self, name: &str, vis: Visibility, obj: ValueObj) {
@@ -359,10 +364,22 @@ impl Context {
 
     fn init_builtin_consts(&mut self) {
         // TODO: this is not a const, but a special property
-        self.register_builtin_immutable_private_var("__name__", Str);
-        self.register_builtin_immutable_private_var("license", mono("_sitebuiltins._Printer"));
-        self.register_builtin_immutable_private_var("credits", mono("_sitebuiltins._Printer"));
-        self.register_builtin_immutable_private_var("copyright", mono("_sitebuiltins._Printer"));
+        self.register_builtin_immutable_private_var("__name__", Str, Some("__name__"));
+        self.register_builtin_immutable_private_var(
+            "license",
+            mono("_sitebuiltins._Printer"),
+            Some("license"),
+        );
+        self.register_builtin_immutable_private_var(
+            "credits",
+            mono("_sitebuiltins._Printer"),
+            Some("credits"),
+        );
+        self.register_builtin_immutable_private_var(
+            "copyright",
+            mono("_sitebuiltins._Printer"),
+            Some("copyright"),
+        );
     }
 
     /// see std/prelude.er
diff --git a/compiler/erg_compiler/context/register.rs b/compiler/erg_compiler/context/register.rs
index b6438409..2d258c2b 100644
--- a/compiler/erg_compiler/context/register.rs
+++ b/compiler/erg_compiler/context/register.rs
@@ -165,7 +165,17 @@ impl Context {
         };
         // already defined as const
         if sig.is_const() {
-            let vi = self.decls.remove(ident.inspect()).unwrap();
+            let vi = self.decls.remove(ident.inspect()).unwrap_or_else(|| {
+                VarInfo::new(
+                    body_t.clone(),
+                    Mutability::Const,
+                    sig.vis(),
+                    VarKind::Declared,
+                    None,
+                    self.impl_of(),
+                    py_name,
+                )
+            });
             self.locals.insert(ident.name.clone(), vi);
             return Ok(());
         }
diff --git a/compiler/erg_compiler/lib/pystd/datetime.d.er b/compiler/erg_compiler/lib/pystd/datetime.d.er
new file mode 100644
index 00000000..93424db1
--- /dev/null
+++ b/compiler/erg_compiler/lib/pystd/datetime.d.er
@@ -0,0 +1,11 @@
+.Date = 'date': ClassType
+.Date.today!: () => .Date
+.Date.min: .Date
+.Date.max: .Date
+.Time = 'time': ClassType
+.DateTime = 'dateTime': ClassType
+.DateTime.today!: () => .DateTime
+.DateTime.now!: (tz := .TZInfo or NoneType) => .DateTime
+.TimeDelta = 'timedelta': ClassType
+.TZInfo = 'tzinfo': ClassType
+.TimeZone = 'timezone': ClassType