Sharepoint - REST API filter by start and end dates using 'today'

Since your "today" variable is a JavaScript date object, you can get the string representation by calling the toISOString() method.

...$filter=StartDate ge datetime'" + today.toISOString() + "' and ...

I answered the question here (not exactly a duplicate, since that was in regards to the Search REST API, and I happened to give an answer for basic REST).

Here is how you filter dates in REST:

$filter=StartDate ge datetime'2014-01-01T00%3a00%3a00'

This filters for items created after 01-Jan-2014, 00:00:00.

So to filter between two date ranges, simply add another condition to the filter:

$filter=(StartDate ge datetime'2014-01-01T00%3a00%3a00') and (EndDate le datetime'2014-04-30T00%3a00%3a00')

This filters for items created between 01-Jan-2014 and 01-May-2014.

Just create your dates in the format: YYYY-MM-DDTHH:MM:SS, and then encode it (or simply use %3a instead of the colons).

This article explains REST filtering based on date, http://itblog.wolthaus.net/2011/12/rest-filter-datetime/.

You'd want to pass in a date in YYYY-MM-DD format.