Hi Sujata and thanks for trying Kibana.
Curious what version of Kibana are you using?
I suspect you are getting the error [strict_date_optional_time||epoch_millis]:
1st you can apply a date filter by just using the Date Picker over near the top right... and click on Absolute and pick a date range.
Or if you want to use the Add Filter on the left hand side, the date needs to be in ISO Format (i.e. same as your JSON above) or MilliSeconds from the epoch, perhaps the docs should link to here instead.
What the strict_date_optional_time means is the Date is mandatory but the Time is optional
So valid formats would be
Date and Time
2019-08-11T14:00:00.000Z
or Date Only
2019-08-11
One word of caution, your date filter should be a subset of the Date Picker time range in the top right, if you date filter that is outside the time in the Date Picker you will get no results... in essence they are "ANDed" . If you clink on the Inspect link you will be the resulting request.