New York law makes service of any process void if service is effectuated on a Sunday (although a recent case called that law into question), and, similarly, prohibits service on a Saturday if the person to be served observes the Sabbath on that day. However, I am not familiar with limitations on times of day in which process (including a subpoena) may be served. As a practical matter, if a process server is being used, you're not going to find many process servers working the graveyard shift. As another practical matter, you're also not going to get many people to open their door to a stranger very late at night.
Process (summons or subpoena) can't be served on the person to be served's sabbath, or at an hour when it might disturb the peace. Process servers can serve at 10 at night or at 6 in the morning (they're supposed to demonstrate that they tried at hours when the person can reasonably be expected to be home) before they can resort to nail-and-mail.
These are statewide rules; they don't just apply in Nassau County.
DISCLAIMER - THIS IS NOT LEGAL ADVICE, AND NO ATTORNEY-CLIENT RELATIONSHIP IS CREATED. IT IS INTENDED SOLELY FOR GENERAL INFORMATION PURPOSES.
Below you will find the only rules regarding the timing of service, but service outside of a 6am-10pm range is frowned upon, and could cause trouble for the client if a court determines that services was made at an off hour willfully and contumaciously.
\u00a7 11 Gen. Bus. Serving civil process on Sunday.
All service or execution of legal process, of any kind whatever, on the first day of the week is prohibited, except in criminal proceedings or where service or execution is specially authorized by statute. Service or execution of any process upon said day except as herein permitted is absolutely void for any and every purpose whatsoever.
\u00a7 13 Gen. Bus. Maliciously serving process on Saturday on person who keeps Saturday as holy time.
Whoever maliciously procures any process in a civil action to be served on Saturday, upon any person who keeps Saturday as holy time, and does not labor on that day, or serves upon him any process returnable on that day, or maliciously procures any civil action to which such person is a party to be adjourned to that day for trial, is guilty of a misdemeanor.