diff --git a/pyproject.toml b/pyproject.toml
index 8e37e7d..199edcd 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -47,11 +47,6 @@ dev = [
 homepage = "https://github.com/HideyoshiNakazone/jambo"
 repository = "https://github.com/HideyoshiNakazone/jambo.git"
 
-[project.optional-dependencies]
-str-fmt = [
-    "isodate>=0.7.2",
-]
-
 
 # POE Tasks
 [tool.poe.tasks]
diff --git a/uv.lock b/uv.lock
index e4184b3..fabfe91 100644
--- a/uv.lock
+++ b/uv.lock
@@ -314,15 +314,6 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/ff/62/85c4c919272577931d407be5ba5d71c20f0b616d31a0befe0ae45bb79abd/imagesize-1.4.1-py2.py3-none-any.whl", hash = "sha256:0d8d18d08f840c19d0ee7ca1fd82490fdc3729b7ac93f49870406ddde8ef8d8b", size = 8769, upload-time = "2022-07-01T12:21:02.467Z" },
 ]
 
-[[package]]
-name = "isodate"
-version = "0.7.2"
-source = { registry = "https://pypi.org/simple" }
-sdist = { url = "https://files.pythonhosted.org/packages/54/4d/e940025e2ce31a8ce1202635910747e5a87cc3a6a6bb2d00973375014749/isodate-0.7.2.tar.gz", hash = "sha256:4cd1aa0f43ca76f4a6c6c0292a85f40b35ec2e43e315b59f06e6d32171a953e6", size = 29705, upload-time = "2024-10-08T23:04:11.5Z" }
-wheels = [
-    { url = "https://files.pythonhosted.org/packages/15/aa/0aca39a37d3c7eb941ba736ede56d689e7be91cab5d9ca846bde3999eba6/isodate-0.7.2-py3-none-any.whl", hash = "sha256:28009937d8031054830160fce6d409ed342816b543597cece116d966c6d99e15", size = 22320, upload-time = "2024-10-08T23:04:09.501Z" },
-]
-
 [[package]]
 name = "jambo"
 source = { editable = "." }
@@ -332,11 +323,6 @@ dependencies = [
     { name = "pydantic" },
 ]
 
-[package.optional-dependencies]
-str-fmt = [
-    { name = "isodate" },
-]
-
 [package.dev-dependencies]
 dev = [
     { name = "coverage" },
@@ -357,11 +343,9 @@ dev = [
 [package.metadata]
 requires-dist = [
     { name = "email-validator", specifier = ">=2.2.0" },
-    { name = "isodate", marker = "extra == 'str-fmt'", specifier = ">=0.7.2" },
     { name = "jsonschema", specifier = ">=4.23.0" },
     { name = "pydantic", specifier = ">=2.12.4" },
 ]
-provides-extras = ["str-fmt"]
 
 [package.metadata.requires-dev]
 dev = [