Bringing in Shabbos Early
There are Jewish communities where the accepted custom is to welcome the Shabbos early on long summer days. Although they do this for the sake of convenience, it is actually a mitzvah to initiate an early Shabbos throughout the year.
(It is relevant to note that there are those who specifically do not practice this custom, choosing to prioritize davening maariv b’zmanah—reciting the evening prayer at the correct time, on a halachic and hashkafic basis.)
To “bring in” Shabbos early in a properly halachic manner, the following should be observed:
Minchah on erev Shabbos should be davened before plag haminchah (one and a quarter halachic hours before sunset) and Maariv, after that time.
There is an extremely narrow window for candle lighting (about ten minutes). Candles may only be lit after plag haminchah, but must take place in advance of the minyan in shul praying Barchu (the beginning of the Maariv service, when Shabbos is accepted by the community).
The nighttime Shema prayer must be recited bizmanah (at its correct time), after tzeis hakochavim (nightfall), regardless of the fact that it was previously recited in shul as part of Maariv.
If it is close to dark, one may not make Kiddush (or begin any meal) before fulfilling the mitzvah of reciting the nighttime Shema. If Kiddush is not made more than a half-hour before tzeis, one must wait to recite the nighttime Shema, as stated above, and only then can they begin their meal. (In addition, there are those with the tradition of not reciting Kiddush between seven P.M. and eight P.M. [daylight saving time; six to seven P.M. in the winter]).
An additional k’zayis of challah (a piece the volume of an olive, see Halacha #235 for a halachic discussion of the measurement) should preferably be eaten after nightfall, if the meal began before that time.