diff --git a/plan/command/update.go b/plan/command/update.go
index 685e1b2..36bf4b6 100644
--- a/plan/command/update.go
+++ b/plan/command/update.go
@@ -84,31 +84,31 @@ func (update *Update) Do() error {
 	if as.Main != "" {
 		e.Title = as.Main
 	}
-	if onStr != "" || atStr != "" {
-		oldStart := e.Start
-		dateStr := oldStart.Format("2006-01-02")
-		if onStr != "" {
-			dateStr = onStr
+	if as.IsSet(FlagOn) || as.IsSet(FlagAt) {
+		on := time.Date(e.Start.Year(), e.Start.Month(), e.Start.Day(), 0, 0, 0, 0, time.UTC)
+		atH := time.Duration(e.Start.Hour()) * time.Hour
+		atM := time.Duration(e.Start.Minute()) * time.Minute
+
+		if as.IsSet(FlagOn) {
+			on = as.GetTime(FlagOn)
 		}
-		timeStr := oldStart.Format("15:04")
-		if atStr != "" {
-			timeStr = atStr
+		if as.IsSet(FlagAt) {
+			at := as.GetTime(FlagAt)
+			atH = time.Duration(at.Hour()) * time.Hour
+			atM = time.Duration(at.Minute()) * time.Minute
 		}
-		newStart, err := time.Parse("2006-01-02 15:04", fmt.Sprintf("%s %s", dateStr, timeStr))
-		if err != nil {
-			return fmt.Errorf("could not parse new start: %v", err)
-		}
-		e.Start = newStart
+		e.Start = on.Add(atH).Add(atM)
 	}
 
-	if frStr != "" { // no check on at, can set a duration with at 00:00, making it not a whole day
-		fr, err := time.ParseDuration(frStr)
-		if err != nil {
-			return fmt.Errorf("%w: could not parse duration: %s", ErrInvalidArg, err)
-		}
-		e.Duration = fr
+	if as.IsSet(FlagFor) {
+		e.Duration = as.GetDuration(FlagFor)
 	}
-	if err := eventRepo.Store(e); err != nil {
+
+	if !e.Valid() {
+		return fmt.Errorf("event is unvalid")
+	}
+
+	if err := update.eventRepo.Store(e); err != nil {
 		return fmt.Errorf("could not store event: %v", err)
 	}
 
@@ -116,7 +116,7 @@ func (update *Update) Do() error {
 	if err != nil {
 		return fmt.Errorf("could not convert event to sync item: %v", err)
 	}
-	if err := syncRepo.Store(it); err != nil {
+	if err := update.syncRepo.Store(it); err != nil {
 		return fmt.Errorf("could not store sync item: %v", err)
 	}