Q. Kevod Horav Shlit’a . Many Poskim maintain that after the destruction of the Beit HaMikdash, Sefirat HaOmer changed and is only a Rabbinic obligation. Is that the reason for women to be exempt?
A. Indeed, many Poskim maintain that after the destruction of the Beis HaMikdosh, Sefirat HaOmer became only a Rabbinic obligation. For this reason, the Mishna Berura (489: 15) writes that many people count sefira during bein hashmashot. (twilight, between sunset and nightfall) In Halacha, this period is considered a “safek yom safek laila” (uncertain time, possibly day or possibly night). Therefore, one can be lenient.
That said, the Mishna Berura (489:14) writes that in any event, it is best to count after nightfall when we are certain it is night. Furthermore, if one counted during Bein Hashmashot, (time of uncertainty if day or night) the Mishna Berura (489:15) recommends repeating the counting without a bracha after nightfall.
Rabbi A. Bartfeld as revised by Horav Hirshman, Horav Dovid Pam, Horav Aharon Miller and Horav Chanoch Ehrentreu and Horav Kalman Ochs Shlit’a.