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You will see as date is being shown for only one post.To solve this follow these Steps:-
1. Login to blogger
2. Click Layout
3. Click Edit HTML tab
4. Check the small box next to the text “Expand Widget Template"
5. Find this code :
<b:if cond='data:post.dateHeader'>
<h2 class='date-header'><data:post.dateHeader/></h2>
</b:if>
6.Remove the code and replace with this one:
<b:if cond='data:post.dateHeader'>
<script>var ultimaFecha = '<data:post.dateHeader/>';</script>
<h2 class='date-header'><data:post.dateHeader/></h2>
<b:else/>
<h2 class='date-header'>
<script>document.write(ultimaFecha);</script>
</h2>
</b:if>
7. Click "SAVE TEMPLATE".
8. Done
Now it will show date for both posts as below.
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Now, all of your posts in the same day will include the date. If you have any problem you can leave your comments.