diff --git a/pandas/_typing.py b/pandas/_typing.py
index e162f7f1662ee..dc3f2f54a54ca 100644
--- a/pandas/_typing.py
+++ b/pandas/_typing.py
@@ -419,6 +419,7 @@ def closed(self) -> bool:
 AlignJoin = Literal["outer", "inner", "left", "right"]
 DtypeBackend = Literal["pyarrow", "numpy_nullable"]
 
+TimeUnit = Literal["s", "ms", "us", "ns"]
 OpenFileErrors = Literal[
     "strict",
     "ignore",
diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index f3de296841510..9e9f28b1dfddb 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -82,6 +82,7 @@
     TimedeltaConvertibleTypes,
     TimeNonexistent,
     TimestampConvertibleTypes,
+    TimeUnit,
     ValueKeyFunc,
     WriteBuffer,
     WriteExcelBuffer,
@@ -2284,7 +2285,7 @@ def to_json(
         date_format: str | None = None,
         double_precision: int = 10,
         force_ascii: bool_t = True,
-        date_unit: str = "ms",
+        date_unit: TimeUnit = "ms",
         default_handler: Callable[[Any], JSONSerializable] | None = None,
         lines: bool_t = False,
         compression: CompressionOptions = "infer",
@@ -2564,11 +2565,11 @@ def to_hdf(
         self,
         path_or_buf: FilePath | HDFStore,
         key: str,
-        mode: str = "a",
+        mode: Literal["a", "w", "r+"] = "a",
         complevel: int | None = None,
-        complib: str | None = None,
+        complib: Literal["zlib", "lzo", "bzip2", "blosc"] | None = None,
         append: bool_t = False,
-        format: str | None = None,
+        format: Literal["fixed", "table"] | None = None,
         index: bool_t = True,
         min_itemsize: int | dict[str, int] | None = None,
         nan_rep=None,