fix: off-by-one in timestamp parsing

Timestamps without dates would infer the correct date based on the local
time. This can lead to bugs where the current local date is different
than the date in the timezone of the original value. Fix this by using
time.Now().In() to adjust the timezone.

Author: nickajacks1

flag_timestamp.go

@@ -86,7 +86,7 @@ func (t *timestampValue) Set(value string) error {
 
 	defaultTS, _ := time.ParseInLocation(time.TimeOnly, time.TimeOnly, timestamp.Location())
 
-	n := time.Now()
+	n := time.Now().In(timestamp.Location())
 
 	// If format is missing date (or year only), set it explicitly to current
 	if timestamp.Truncate(time.Hour*24).UnixNano() == defaultTS.Truncate(time.Hour*24).UnixNano() {