ProPublica’s Sebastian Jones notes what for us has been one of the most maddening features of campaign finance data: the dates don’t mean very much at all. Campaigns report when they receive money, and political action committees report when they donate it. In theory, those dates should match, but as Jones points out, they don’t:

The Federal Election Commission [3] requires politicians to disclose the dates and amounts of contributions they receive in periodic reports. Corporate and special interest political action committees (PACs) are also required to file reports with the FEC, disclosing the money they contribute. “In a perfect world, they match up,” FEC spokesperson Mary Brandenberger told ProPublica.

But when we compared those records for the Springsteen fundraisers, two problems emerged. Most of the dates the politicians said they got the money differed significantly from the dates the PACs said they disbursed their contributions. And many of the expenditures the lawmakers disclosed in their reports were so vaguely described that they were almost meaningless.

We began our search with an advantage, because some invitations to the Springsteen fundraisers were leaked to the nonprofit Sunlight Foundation’s Party Time website. Sunlight’s list represents only a small fraction of the fundraisers held in Washington each year, so there may have been more fundraisers at Springsteen concerts – there’s simply no way of knowing for sure.

With the invitations in hand, we began plowing through the records, but in no time at all, something seemed odd: the lawmakers reported surprisingly few contributions on the dates of the concerts —May 18 and Nov. 2, 2009. Even expanding our search to include contributions made near the dates of the fundraisers yielded few additional matches.

That’s a problem we’ve had since we launched the Party Time site. I’m told by some people who work in campaigns that “date” is interpreted rather loosely–it can be the date that a contribution was received, the date it was deposited in the bank, the date that the information was entered into the campaign’s internal databases for tracking contributions, or some other date altogether. Compounding the difficulty is the fact that lobbyists and others who attend fundraisers don’t necessarily write their checks on the day of the fundraiser, lobbyists have told me. They might show up with a check. They might have sent it in a month in advance. And they might send it two weeks after the event. So following the money from dates is difficult–really we’re operating within quarters or half-years, and can’t get any more precise than that.