Between the hours of 6:00 AM and 10:00 PM, if the outside temperature falls below 55 degrees, the inside temperature is required to be at least 68 degrees Fahrenheit;

and

Between the hours of 10:00 PM and 6:00 AM, if the temperature outside falls below 40 degrees, the inside temperature is required to be at least 55 degrees Fahrenheit.

For Further Information, please follow the below link to nyc.gov

http://www.nyc.gov/html/hpd/html/tenants/heat-and-hot-water.shtml