Many websites use this format for a copyright notice:

Copyright 2009-2016 by Martin Brown. All Rights Reserved.

While there is no specific provision in copyright law for using a range of years rather than a single year, such notices do meet the three elements of 17 U.S.C. §401(b): 1. the word “Copyright,” “Copr.” or the © symbol; 2. the year of first publication; and 3. the name of the copyright owner. Thus, these notices are presumed to be valid. Using a range of dates makes sense in a general copyright notice for a website that includes material published during different years. Photographers may also want to include individual copyright notices for each photograph, and those notices should use the year that the photograph was first published.

Keep things in perspective. Copyright notice is not a legal requirement. You could have no copyright notice whatsoever and your photographs would still be protected by copyright. The only purpose of a copyright notice is to inform viewers of an image that it is under copyright protection, and prevent them from claiming ignorance.