The service alerts for this coming Halloween weekend and week are the same as for the previous. From 11:45 p.m. tomorrow (Friday, October 28) to 5:00 a.m. Monday, October 31 there will be no 4 or 5 trains running in either direction at Borough Hall. Use 2, 3, A, C, R, or (late night) N trains as options.
The following work week (Monday, October 31 to Friday, November 4) each night from 11:45 p.m. to 5:00 a..m there will be no service in either direction at Court street or on the R/N platforms at Borough Hall. Use the 4 as an option. On these same nights from 10:00 p.m. to 5:00 a.m. F trains in both directions will be diverted to the A/C line, which means no service in either direction at the York Street station in DUMBO. Use the High Street station as an option.
Incidentally, today is the 112th anniversary of subway service in New York City.