I got a calendar in the mail from some charity. It lists the times to begin and end the sabbath. It's written in Hebrew. Here's this week's:
candle-lighting [time, before the sabbath]
the end of the holy sabbath
[according to] the kabbalist 6:17 p.m.
[according to] Rabenu Tam 6:56 p.m.
Which kabbalist is this, and where do we see in his writings that he holds of this earlier time for ending the sabbath?