Question:

We have a Chasan in Shul who just got married for his second time with a woman who was also previously married. For how many days should we omit Tachanun when he is present by the Minyan?

Answer:              

Tachanun is omitted for three days after the wedding, for a period of 72 hours beginning from the end of the Chuppah. Thus, if the Chuppah ended on Monday at 7:00 PM, then Tachanun is omitted on Tuesday, Wednesday, and Thursday until 7 PM.

Explanation: The amount of days for omission of Tachanun by the congregation when in the presence of a Chasan is commensurate to the amount of days that the Chasan is required to keep the Mitzvah of Simcha, to rejoice his new bride. By a Zivug Sheiyni, which is defined as any individual who is only obligated to keep three days of Simcha after the wedding, and only one day of Sheva Brachos, Tachanun is omitted for three days after the wedding, for a period of 72 hours beginning from the end of the Chuppah. This would include a widow who marries a widower, or a widow who marries a divorcee, or a widower or divorcee who marries a divorcee or widow. If, however, it is the first marriage for the groom, or if it is his second marriage but he is marrying a woman who was never yet married and is a Besula, and hence seven days of Sheva Brachos and Simcha are being kept, then Tachanun is to be omitted for a full seven day period

Sources: See Shiyurei Kneses Hagedola 131:16; Shalmei Tzibur p. 151; Peri Hadama 1:16 that so is custom of Jerusalem; Kesher Gudal 131:20; Beis Oveid 6; Magen Giborim 131:16; M”B 131:26; P”M 131 M”Z 10;  Kaf Hachaim 131:71; Ketzos Hashulchan 24:6; Halacha Berura Yosef 131:29