diff --git a/README.md b/README.md
index 7b46b44..ae6ced0 100644
--- a/README.md
+++ b/README.md
@@ -7,3 +7,84 @@
 [license]: https://github.com/nukokusa/koyomi/blob/master/LICENSE
 
 Koyomi is a simple schedule client for Google Calendar.
+
+## Usage
+
+```
+Usage: koyomi <command>
+
+Flags:
+  -h, --help                            Show context-sensitive help.
+      --credential="credential.json"    JSON credential file for access to calendar
+      --loglevel="INFO"                 Logging level: DEBUG, INFO, WARN, ERROR
+  -v, --version                         Show Version
+
+Commands:
+  list --calendar-id=STRING --start-time=STRING --end-time=STRING
+    List events
+
+  create --calendar-id=STRING --start-time=STRING --end-time=STRING
+    Creates an event
+
+  update --calendar-id=STRING --event-id=STRING
+    Updates an event
+
+  delete --calendar-id=STRING --event-id=STRING
+    Deletes an event
+```
+
+### List Events
+
+```
+Usage: koyomi list --calendar-id=STRING --start-time=STRING --end-time=STRING
+
+List events
+
+Flags:
+      --calendar-id=STRING              Calendar identifier
+  -s, --start-time=STRING               The start time of the event
+  -e, --end-time=STRING                 The end time of the event
+```
+
+### Creates an Event
+
+```
+Usage: koyomi create --calendar-id=STRING --start-time=STRING --end-time=STRING
+
+Creates an event
+
+Flags:
+      --calendar-id=STRING              Calendar identifier
+      --summary=STRING                  Title of the event
+      --description=STRING              Descriptuon of the event
+  -s, --start-time=STRING               The start time of the event
+  -e, --end-time=STRING                 The end time of the event
+```
+
+### Updates an Event
+
+```
+Usage: koyomi update --calendar-id=STRING --event-id=STRING
+
+Updates an event
+
+Flags:
+      --calendar-id=STRING              Calendar identifier
+      --event-id=STRING                 Identifier of the event
+      --summary=STRING                  Title of the event
+      --description=STRING              Description of the event
+  -s, --start-time=STRING               The start time of the event
+  -e, --end-time=STRING                 The end time of the event
+```
+
+### Deletes an Event
+
+```
+Usage: koyomi delete --calendar-id=STRING --event-id=STRING
+
+Deletes an event
+
+Flags:
+      --calendar-id=STRING              Calendar identifier
+      --event-id=STRING                 Identifier of the event
+```
diff --git a/go.mod b/go.mod
index a6d06b9..e88627a 100644
--- a/go.mod
+++ b/go.mod
@@ -3,6 +3,7 @@ module github.com/nukokusa/koyomi
 go 1.20
 
 require (
+	github.com/Songmu/flextime v0.1.0
 	github.com/alecthomas/kong v0.7.1
 	github.com/google/go-cmp v0.5.9
 	github.com/hashicorp/logutils v1.0.0
diff --git a/go.sum b/go.sum
index a41dae5..dbce09a 100644
--- a/go.sum
+++ b/go.sum
@@ -6,6 +6,8 @@ cloud.google.com/go/compute/metadata v0.2.3 h1:mg4jlk7mCAj6xXp9UJ4fjI9VUI5rubuGB
 cloud.google.com/go/compute/metadata v0.2.3/go.mod h1:VAV5nSsACxMJvgaAuX6Pk2AawlZn8kiOGuCv6gTkwuA=
 cloud.google.com/go/longrunning v0.4.1 h1:v+yFJOfKC3yZdY6ZUI933pIYdhyhV8S3NpWrXWmg7jM=
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
+github.com/Songmu/flextime v0.1.0 h1:sss5IALl84LbvU/cS5D1cKNd5ffT94N2BZwC+esgAJI=
+github.com/Songmu/flextime v0.1.0/go.mod h1:ofUSZ/qj7f1BfQQ6rEH4ovewJ0SZmLOjBF1xa8iE87Q=
 github.com/alecthomas/assert/v2 v2.1.0 h1:tbredtNcQnoSd3QBhQWI7QZ3XHOVkw1Moklp2ojoH/0=
 github.com/alecthomas/kong v0.7.1 h1:azoTh0IOfwlAX3qN9sHWTxACE2oV8Bg2gAwBsMwDQY4=
 github.com/alecthomas/kong v0.7.1/go.mod h1:n1iCIO2xS46oE8ZfYCNDqdR0b0wZNrXAIAqro/2132U=