tzais13Point5Minutes
Tzais of the לוח המאור אור החיים: 13.5 minutes zmaniyos, or 0.225 of a shaah zmanis, after sunset. This is the tzais the calendar prints all year round.
Note that this is a very early tzais, especially in the winter and far from the equator. It should not be relied on for the end of Shabbos or anything else of consequence without asking a Rav.