They accept after Pesach and Sukkos; usually not for Elul Zman. For Winter Zman, no dating until Tu B’Shvat. For Summer Zman, no dating until Tisha B’Av (official end of zman).
If you’re dating a girl before the zman starts, you can submit her initials to the office and continue dating her.
If you break the freezer rules, the Roshei Yeshiva will not come to your wedding.