We are obligated to add "from the profane to the sacred" by accepting Shabbath before sunset (See Rashi Bereshith:2:2). Since women accept Shabbath upon themselves by lighting the Shabbath candles, obviously they have to light before sunset.
There are different customs as to when a woman should light her Shabbath candles. In Yerushalayim, for example, the horn (Shofar) is blown 40 minutes before sunset. According to the ruling of Hakham Yoseph Hayyim 'a"h, the Ben Ish Hai, it is best to light 30 minutes before sunset. In the US, most calendars state candle lighting time 18 minutes before sunset.
As discussed previously, candle lighting time is considered to be an עת רצון, a time when our prayers are accepted. It is a special time of connecting with our Father in Heaven, asking Him for what every Jewish woman should pray for: to merit to see her children become Torah scholars and illuminate the world with their Torah knowledge. Obviously, even if a woman does not have children, she must still light the candles for Shabbath, because it does other Tiqqunim (rectifications).
While during the week there is a constant struggle between the physical and spiritual, the profane and the holy, Shabbath exemplifies that which is holy and spiritual. What better time is there to experience this elated feeling than when we stand in front of the candles?
I know that for many women it is a weekly challenge to change into a beautiful Shabbath outfit, knowing that all the work is complete, and stand in front of the candles, on time, with calmness and inner peace. I would not like any one of us to be deprived of these very special moments. I believe that with a bit of planning and early preparation you can be the queen welcoming Shabbath the Queen into your home.