It’s the oldest trick in the PR playbook: get your bad news out on a Friday and leave early for the weekend.

Strangely, this practice still holds, even in today’s continuous news environment.  Just look at the news today from SAC Capital and J.P. Morgan. 

J.P. Morgan executives are testifying today before a Senate committee investigating the firm’s “London Whale” trading loss.  It’s the latest chapter in a long-running scandal, but it’s unlikely to produce many new revelations.  It’s embarrassing for the bank, but the headlines likely will subside by Monday.

Likewise, a SAC Capital fund announced today it has settled insider-trading charges for slightly more than $600 million.  That, too, will produce a storm of coverage today and tomorrow before fading from view.

Of course, a firm can’t always control when this kind of news will happen, particularly when regulators set the timing. But where it can exert some influence, firms usually try to push such announcements to late in the week.

This might seem unusual in an age when online news social media operate around the clock, but it shows how enduring the conventions of the financial week remain. Until US financial markets and Congressional offices remain open continuously, Friday will still punctuate the working week and draw a line under its news.

Weekend newspapers in the US remain relatively free of business reporting.  With rare exceptions, major business news does not break in the weekend editions of the two national newspapers – the New York Times and The Wall Street Journal – and only one (the Times) produces a Sunday edition (that is mostly written by the previous Friday).

In the UK by contrast (where many national dailies compete fiercely), Saturday and Sunday are rich days for business coverage, with breaking news, investigative features and exclusive interviews.  There, it’s a full seven-day news cycle, with barely a dull moment.

Of course, even talking about a news “cycle” today seems a little antiquated, conjuring up images of ink-stained newsboys on street corners.  But news still follows an arc, just as it always has: a brief period of intense coverage followed by a gradual decline.

Thanks to these forces, J.P. Morgan and SAC Capital will have to face rough coverage from the media for just a day or two.  And without more news coverage to feed it, the blogosphere will remain relatively quiet, too.

By Monday, other news will grab our attention.  With any luck, it will be from a firm in the financial industry, which has generously provided so many jaw-dropping stories over the past five years.