Rahukaal is the time in day which is called the time of Rahu . Rahukaal varies with date and place. That means rahukaal keeps changing for different days and is also different for different places(difference is due to the change in standard time). Any holy , auspicious or good work should never be started during the rahukaal. Rahukaal lasts for nearly two hours. As per Indian mythology and vedic shastras it is recommened to avoid doing good things in this time span.
Acharya Indu Prakash Ji has provided the Rahukaal for major cities as under which is updated every month. 

If you want to see the rahukaal for your city kindly visit http://www.acharyainduprakash.com/en/services/rahukaal.html

website of Acharya Ji is : www.acharyainduprakash.com http://www.acharyainduprakash.com/