The closures started on 11/22/22 and will last until 3/31/23. Last evening was the first time I ran into them.
https://www.nps.gov/rocr/learn/news/national-park-service-announces-2022-2023-deer-management-operations-for-rock-creek-park.htm
According to the park Resource Manager:
We do not give out information on specific operation days and times, however, as a measure of protection for park staff and the sharpshooting operations.
And even though the new release above states that Beach Drive and Ross Drive may be closed between 6:45 pm and 4 am, yesterday (11/28) both roads (along with Ridge Road) were closed before 5:45 pm. The only option was to take Morrow Drive and Blagden Ave.