When you upload a new blogspot template from third party designer to your blogspot and found that the date for your post was “undefined”. This is actually an error, then you have to correct it. This “Undefined” error will appeared in every post instead of the blog post date.
The reason for this error is the blog timestamp does not match with the one required. To fix this error, you have to follow this simple steps:
1. Loging to your blogger dashboard
2. Go to Setting
3. Go to Formatting
4. Modify the Date Header Format, Archive Index Date Format and Timestamp Format as below.
5. Click Save button.