A swing timer WA for Retribution paladins that supports Seal Twisting.
Simply change seals or use your seal twist macro on or after the green mark on the swing timer in order to successfully seal twist.
The red line (optional, activated by enabling it under User Options) signifies the last possible moment you can activate Seal of Command, before you can no longer twist on that swing due to Seal of Command's global cooldown. By default it's at 1.5 seconds before your swing, though it moves around depending on your spell haste value.