the date your documents were received and registered...

it's also the date you'll use in monitoring the visa bulletin to see how near you are to being attended to

Godsent thanks

godsent how can't I check on visa bulletin to see if I'm close or not ?

visit uscis page and scroll the tab to visa bulletin

@godsend how can't I check my priority date is current?

look at your notice of action....you'll see it there