The earliest of date of filing of the I-130, the Labor Certification, the I-140, or I-360 is the “Priority Date” for your case. This date is important because it determines your place in line for an immigrant visa number. This date is used whenever the visa category under which you are immigrating is backlogged.
The Department of State is responsible for publishing the Priority Date Visa Bulletin showing the cut-off dates for which there are visas available. Because the bulletin lists “cut-off” dates, only dates prior to the listed dates are current.
Priority dates can advance, and they can retrogress (move backwards). Whether the dates advance or retrogress depends on several factors, including the number of visas available, and the number of requests that the State Department receives for those visas. The Department of State’s goals are to make sure that all the available visas are used by the end of the Federal fiscal year, and to ensure that those who started the process first, get to complete it first.
Whether priority dates will move, and whether they will move forwards or backwards, cannot be predicted.
A more detailed explanation on how the progress of the Priority Dates is determined can be found at this link.
The links below give you Eng & Nishimura’s enhanced priority date listings.