Invoice API Feature: method for "updated since date"

In my application and, I would think, in those of most other developers, I the developer have no use for getting all of the invoices (or customers or items or payments made, etc.) after the first time. Too much data exchange. Just give me what has changed since I last checked.

I suggest creating a GET method something like https://invoice.zoho.com/api/[invoices]/modified-after/ where one of the parameters is a time stamp string (i.e. yyyy-mm-dd hh:ii:ss). The response would list all [invoiced] modified since this date/time.

You could also include a similar method: GET method something like https://invoice.zoho.com/api/[invoices]/modified-before/ where one of the parameters is a time stamp string (i.e. yyyy-mm-dd hh:ii:ss).

I suggest that many developers would like this feature because I assume that a main goal of many integrated apps is syncing data (invoices, payments, customers... whatever). Without a method like I described, the only way I can really synchronize data is to regularly GET all of my data and go through each, say invoice, field by field, comparing to my local data. That is an extremely laborious and resource-heavy process. Why not just tell me what has changed since 2010-09-20 08:20:10 (i.e. the time I know I last checked)? Then you (the API) send less data and I process less data.

If there already exists a method like this and I missed it, please tell me as the lack of this single feature may be a deal-breaker for me and my app. I know xero has a parameter for this (see http://blog.xero.com/developer/api/Invoices/#GET) . So does FreshBooks (see http://developers.freshbooks.com/api/view/invoices/#invoice.list ).

Or perhaps there is a better way to sync data than the painful process I described above. If anyone knows of one, please let me know.

Thanks.