Search between two dates with ISO8601 format - angularjs

Question

Using angularjs, dynamodb as DB here.
I have a form where user saves some data. I save my "CreateOn" date in my dynamo db as:
DateTime.UtcNow.ToString("o");
//This saves date in DB as:2018-08-21T12:58:08.7823906Z
Storing like this because dynamo db requires dates (string) to stored in ISO8601 format if you want to use between operator to search for date range.
Now I have a search filters on my page which is basically an angular calendar. When the user selects the date in the calendar( start and end date) I want to get the data back based on the selected date. Here I am using moment to pass the calendar selected date to my api call as:
moment(createdOn).toISOString()
Eg: If they select the Today's date in the calendar I pass the selected date
(Tue Aug 21 2018 00:00:00 GMT-0400 (Eastern Daylight Time)) to the above function
The result of passing this date to moment(createdOn).toISOString() is
2018-08-21T04:00:00.000Z
The search condition at dynamo db is:
conditions.Add(new ScanCondition("CreatedOn", ScanOperator.Between, startDate, endDate ));
If the user selects from the calendar the start date as "08-20-2018" (2018-08-20T04:00:00.000Z) and the end date is "08-21-2018"(2018-08-21T04:00:00.000Z), the code all the data created b/w these 2 dates.
Now the issue is if they select same start and end date then the code does not returns any data, I believe because the start and end date is "2018-08-21T04:00:00.000Z" and the time part of this is all 0000 etc.
My question is how can I convert the date from my calendar ie my end date to correctly reflect the the end time which they select. I havent used ISO8601 format before so not sure how can I do so.
Thanks

Answer 1

You don't need moment for this. You can zero out the time using a Date in the following way.
const date = new Date('2018-08-21T12:58:08.7823906Z')
date.setUTCHours(0)
date.setUTCMinutes(0)
date.setUTCSeconds(0)
date.setUTCMilliseconds(0)
Then you can simply use toISOString() to format the date.
date.toISOString()
// returns '2018-08-21T00:00:00.000Z'
If you don't want to zero out the time, and instead want to set some specific time, you can use a similar approach, just substitute the 0 with whatever time you want.
Some other things to note: DynamoDB doesn't require any specific formatting for dates. DynamoDB simply does a string or number comparison depending on what the field is defined as. You could store your dates in DynamoDB as integers or another string format if you feel that would be easier to work with.
Also, I'm not sure how your table is setup but make sure that your "CreateOn" field is the Range key and that you are using Query, not Scan. Using the Scan operation doesn't scale well.