Add whatsnew item

dwillmer · dwillmer · commit 5e8e23b43dcf · 2017-07-19T23:25:12.000+01:00
diff --git a/doc/source/whatsnew/v0.21.0.txt b/doc/source/whatsnew/v0.21.0.txt
@@ -186,6 +186,7 @@ Sparse
 Reshaping
 ^^^^^^^^^
 - Joining/Merging with a non unique ``PeriodIndex`` raised a TypeError (:issue:`16871`)
+- Merging with categorical date columns raised a TypeError (:issue:`16900`)
 
 
 Numeric
