how to write GAE search query using date?

This is my data store.

```
Class Property(db.Model):
    createdDate=db.DateTimeProperty(auto_now_add=True)

```

i want to display the records in last sevendays. am tring this,

```
sevendays = datetime.now() - timedelta(hours=168)

```

getting correct result for date(7days), and i passed search query in my URL like this,

```
<a href="/search?search=PropertyCaseType+%3D+Enquiry+AND+PropertyStatus+%3D+Open+AND+createdDate+%3E+sevendays" class="list-group-item">
                                <i class="fa fa-question-circle fa-fw"></i> New Enquires
                                <span class="pull-right text-muted small"><em>
                                    {% if countEnquiryOpen %}
                                        {{ countEnquiryOpen }}
                                    {% else %}
                                        0
                                    {% endif %}

                                </em>
                                </span>
                            </a>

```

above href= encode query is : 
 PropertyCaseType = Enquiry AND PropertyStatus = Open AND createdDate > sevendays

createdDate > sevendays is not working , otherwise query working fine and getting correct results.

how to do this , friends help me