Why won't GitHub recognize this as zlib?

LICENSE.txt

@@ -1,4 +1,4 @@
-Copyright (c) 2012-2021 Ryan C. Gordon <icculus@icculus.org>
+Copyright (c) 2012 Ryan C. Gordon <icculus@icculus.org>.
 
 This software is provided 'as-is', without any express or implied
 warranty.  In no event will the authors be held liable for any damages
@@ -15,4 +15,3 @@ freely, subject to the following restrictions:
 2. Altered source versions must be plainly marked as such, and must not be
    misrepresented as being the original software.
 3. This notice may not be removed or altered from any source distribution.
-