Question: We will participating in a group Shabbat away from home, and the times of the meals have been set by the place we will be at. What is the earliest time we can eat our Shabbat Meal?

Answer: It must be clearly understood that the Seudat Shabbat must be eaten after Plag Hamincha which is approximately 1hour 15 minutes before sunset/shekiya (in a perfect day which has a 12 hour day and a 12 hour night); neither can one accept Shabbat upon oneself by lighting candles as well as by reciting the Psalm of Mizmor Shir Leyom Hashabbat - before Plag Haminchah.

And as long as it is after Plag Hamincha not only is it permissible to add hours to Shabbat but it is also a positive fulfillment of the necessity of increasing holiness within our lives תוספת קדושה which we derive from Yom Kippur, where it is Biblically mandated that we begin Yom Kippur when it is still the 9th of Tishrei, even before the 
advent of the 10th of Tishrei with sunset.