diff --git a/go.mod b/go.mod
index f9ed364..07a38cf 100644
--- a/go.mod
+++ b/go.mod
@@ -3,6 +3,7 @@ module github.com/Life-USTC/CLI
 go 1.26.0
 
 require (
+	github.com/Life-USTC/client-core v0.1.0
 	github.com/PuerkitoBio/goquery v1.13.0
 	github.com/charmbracelet/bubbles v1.0.0
 	github.com/charmbracelet/bubbletea v1.3.10
diff --git a/go.sum b/go.sum
index 9c5449a..a44c64b 100644
--- a/go.sum
+++ b/go.sum
@@ -1,3 +1,5 @@
+github.com/Life-USTC/client-core v0.1.0 h1:kAtPq/m/W7SEMiR9KG/m2F0ZRyBXnzkNbfoKa4mMDmc=
+github.com/Life-USTC/client-core v0.1.0/go.mod h1:2SgYKZ3hbEFEigNGPdbfFS2m149evVw2t/mEjA/S/LM=
 github.com/PuerkitoBio/goquery v1.13.0 h1:mqHbjD7Jmnul4DTR24LKTjo1uUmHUh072kteGV+xpFM=
 github.com/PuerkitoBio/goquery v1.13.0/go.mod h1:Hip5mdBL8K2wEGKJdr27sRaNwIdDajmCwB/ExUPwW+g=
 github.com/RaveNoX/go-jsoncommentstrip v1.0.0/go.mod h1:78ihd09MekBnJnxpICcwzCMzGrKSKYe4AqU6PDYYpjk=
diff --git a/internal/cmd/youngutil/youngutil.go b/internal/cmd/youngutil/youngutil.go
index 8d05091..0e7b8e9 100644
--- a/internal/cmd/youngutil/youngutil.go
+++ b/internal/cmd/youngutil/youngutil.go
@@ -11,6 +11,7 @@ import (
 	"time"
 
 	"github.com/Life-USTC/CLI/internal/cmd/cmdutil"
+	"github.com/Life-USTC/client-core/calendar"
 )
 
 const (
@@ -249,20 +250,12 @@ func DateRange(view DateView, anchor string, now time.Time) (string, string, err
 		return "", "", err
 	}
 	switch view {
-	case DateDay:
-		formatted := formatDate(date)
-		return formatted, formatted, nil
-	case DateWeek:
-		offset := (int(date.Weekday()) + 6) % 7
-		start := date.AddDate(0, 0, -offset)
-		return formatDate(start), formatDate(start.AddDate(0, 0, 6)), nil
-	case DateMonth:
-		start := time.Date(date.Year(), date.Month(), 1, 0, 0, 0, 0, Shanghai)
-		end := start.AddDate(0, 1, -1)
-		return formatDate(start), formatDate(end), nil
+	case DateDay, DateWeek, DateMonth:
 	default:
 		return "", "", fmt.Errorf("unsupported date view %q", view)
 	}
+	bounds, err := calendar.Bounds(calendar.Period(view), date, time.Monday)
+	return bounds.From, bounds.To, err
 }
 
 func anchorDate(anchor string, now time.Time) (time.Time, error) {
@@ -276,7 +269,3 @@ func anchorDate(anchor string, now time.Time) (time.Time, error) {
 	}
 	return date, nil
 }
-
-func formatDate(date time.Time) string {
-	return date.In(Shanghai).Format("2006-01-02")
-}