Update date in copyright line
diff --git a/library/hmac_drbg.c b/library/hmac_drbg.c
index 5c4ee6d..072f5f7 100644
--- a/library/hmac_drbg.c
+++ b/library/hmac_drbg.c
@@ -1,7 +1,7 @@
 /*
  *  HMAC_DRBG implementation (NIST SP 800-90)
  *
- *  Copyright (C) 2014, ARM Limited, All Rights Reserved
+ *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
  *
  *  This file is part of mbed TLS (https://tls.mbed.org)
  *