polishing

Author: he-yang

source/about.md

@@ -18,7 +18,6 @@ This add-in is available at the Microsoft store- Appsource, which can be accesse
  profeatures.md
  termsofuse.md
  privacy.md
- about.md
  contact.md
 
 

source/index.rst

@@ -183,6 +183,7 @@ The Date Format specifies how to convert date values in Excel:
 2. `String, ISO 8601 (YYYY-MM-DDTHH:mm:ssZ)`: Converts to ISO 8601 formatted string
 
 > Note: The Date Format feature only work, if you add $date$ as surfix in your Excel Datasheet first row.
+> Note: Excel can not render Dates before 1990-01-01 as Date format, so you may find that cell be interpreted as String format.
 > For instance, if you want to convert the Birthday column to ISO8601 format, you should add $date$ as surfix in the column header, see example below.
 
 **Example Excel sheet**