Today is the 18th of Tamuz, 5770
Ben haMetzarim is a period of 3 weeks, from the 17th of Tammuz until the 9th of Av (July 19th/20th). As we have explained, it took the Babylonians three weeks from the time the Babylonian army breached the walls of Yerushalaim until they finally burned and destroyed the Bet haMikdash. During this time, besides the massive destruction and pillaging of the Holy city, thousands of people were tortured and killed.
That is why during these 21 day period we observe certain traditions of mourning that build up as we get closer to Tisha BeAv.
SHEHECHEYANU for NEW FRUITS: Eating a new fruit that will require us to say the blessing Shehecheyanu during the three weeks should be done only on Shabbat.
WEDDINGS: No weddings take place during the three weeks.
ENGAGEMENTS: Saying Shir Lamaalot with no music is allowed until Rosh Chodesh Av (July 11th /12th).
MUSIC: We refrain from listening to music during the three weeks. Religious music is allowed, if it is not live music.
CLOTHING: It is not permitted to buy new clothing, except: 1. For a bride or groom that will get married after Tisha BeAv. 2. If the article is on sale and it will be substantially more expensive after Tisha BeAv. Our tradition is also to not buy gold and/or Jewelry from Rosh Chodesh Av.
HAIRCUT: It is permitted to get a haircut only until Rosh Chodesh Av. Our Minhag is that men do not shave from the Shabbat before Tisha BeAv until after Tisha BeAv.
NEW HOUSE: it is permitted to close or move into a new house until Rosh Chodesh Av.
EATING MEAT: Our tradition is to refrain from meat after Rosh Chodesh Av until the day after Tisha BeAv. A person who is sick or weak or a woman during the first 30 days after giving birth, are allowed to eat meat. Although chicken would be preferable to meat. Fish is allowed during the three weeks.
The above mentioned are some examples of the basic traditions that we follow on these days of mourning (for more information ask one of our community Rabbis).