Gimmel Tammuz (3rd Tammuz) was the day when Joshua told the Sun and Moon to stand still. You can read about this event in the book of Joshua chapter 10. In this book Jethro discusses this event and how it may have been possible for the Sun and Moon to have stood still. He shows how this event has a Messianic message and how it is linked to two other events that took place fairly recently. One was the freeing from prison of Rabbi Yosef Yitzchak Schneersohn on 3rd Tammuz (corresponding to 3rd July 1927) and the other is the passing of Rabbi Menachem Mendel Schneerson on the 3rd Tammuz (12th June 1994). Jethro uses both Hebrew and English Gematria to show these links and how this day is connected to both concealment and revelation.