diff --git a/util/time.go b/util/time.go
--- a/util/time.go
+++ b/util/time.go
@@ -1,52 +1,3 @@
 package util
 
-import (
-	"fmt"
-	"time"
-)
-
 const ISO8601 = "2006-01-02T15:04:05.000Z"
-
-const ISO8601_milli = "2006-01-02T15:04:05.000000Z"
-
-const ISO8601_numtz = "2006-01-02T15:04:05.000-07:00"
-
-const ISO8601_numtz_milli = "2006-01-02T15:04:05.000000-07:00"
-
-const ISO8601_sec = "2006-01-02T15:04:05Z"
-
-const ISO8601_numtz_sec = "2006-01-02T15:04:05-07:00"
-
-func ParseTimestamp(s string) (time.Time, error) {
-	t, err := time.Parse(ISO8601, s)
-	if err == nil {
-		return t, nil
-	}
-
-	t, err = time.Parse(ISO8601_milli, s)
-	if err == nil {
-		return t, nil
-	}
-
-	t, err = time.Parse(ISO8601_numtz, s)
-	if err == nil {
-		return t, nil
-	}
-
-	t, err = time.Parse(ISO8601_numtz_milli, s)
-	if err == nil {
-		return t, nil
-	}
-
-	t, err = time.Parse(ISO8601_sec, s)
-	if err == nil {
-		return t, nil
-	}
-
-	t, err = time.Parse(ISO8601_numtz_sec, s)
-	if err == nil {
-		return t, nil
-	}
-
-	return time.Time{}, fmt.Errorf("failed to parse %q as timestamp", s)
-}
diff --git a/util/time_test.go b/util/time_test.go
deleted file mode 100644
--- a/util/time_test.go
+++ /dev/null
@@ -1,20 +0,0 @@
-package util
-
-import "testing"
-
-func TestTimeParsing(t *testing.T) {
-	good := []string{
-		"2023-07-19T21:54:14.165300Z",
-		"2023-07-19T21:54:14.163Z",
-		"2023-07-19T21:52:02.000+00:00",
-		"2023-07-19T21:52:02.123456+00:00",
-		"2023-09-13T11:23:33+09:00",
-	}
-
-	for _, g := range good {
-		_, err := ParseTimestamp(g)
-		if err != nil {
-			t.Fatal(err)
-		}
-	}
-}