It's official... again. We're back in bear market territory. Thanks to last week's rout, the S&P 500 (^GSPC 1.26%) now sits a little more than 23% below its late-December peak. The Dow Jones Industrial Average (^DJI 1.18%) is now down 20% from its early January high, reaching new lows for the year on Friday. The Nasdaq Composite (^IXIC 1.99%) isn't faring any better. And almost everyone senses lower lows aren't a distinct possibility now that the sell-off has gained some momentum. In short, it's difficult to even think about being a buyer here, as it's tantamount to catching a falling knife. If your timing is perfect, it's a clever trick. If your timing is off, it could hurt -- a lot.

The thing is, this is exactly when you should be buying stocks, even knowing we may not have reached the ultimate bottom just yet.

Historically, the calendar is working in your favor

It's an admittedly tough idea to digest at this time. The market's tanking, interest rates are rising, and little seems to be curbing rampant inflation. In short, the foreseeable future looks grim.

As investing legend Warren Buffett explains it, though: "Be fearful when others are greedy, and greedy when others are fearful." Stocks recover sooner than most of us suspect they should, and offer no warning as to when they've begun a new bull market.

There's more to the don't-worry-about-short-term-noise sermon than words of wisdom served up by the Oracle of Omaha, however. There's data to back up the assertion that we're likely closer to a major low than not.

Some of this data is served up by mutual fund company Hartford. Its number-crunching indicates that the average bear market since 1929 has lasted 289 days, or 9.6 months. Counting back to the Dow's and the S&P 500's highest highs would place any turnaround at some point late this month or early next month.

The market has a mind of its own, of course, and is going to do what it's going to do with no real regard for the calendar. A tendency is a tendency all the same, though. And in this same vein, the market's also got a curious tendency to end bear markets and start new bull markets in the month of October... albeit often after one last October rout that serves as a capitulation.

Don't miss the beginning of the bounce

With or without the calendar's help, however, you're still better served by stepping into stocks here even if there's more downside left to dish out.

As was noted, stocks don't send out any warning or notice of an impending recovery. They usually just happen, and rather abruptly.

The thing is, you don't want to miss out on any part of a rebound, as the first few days of a new bull market are often explosively bullish. Brokerage firm Edward Jones says that of the five most recent transitions out of bear markets, the S&P 500 rallied an average of 25% during just the first three months of these new bull markets. Other numbers from Hartford underscore the idea, suggesting that around one-third of a bull market's very biggest daily gains materialize during the first two months of that bull run.

Unless you happened to sell all of your holdings right at the end of last year, you can't really afford to miss out on that important piece of any turnaround... whenever it might take shape.

It's all about the timeframe

There's a much bigger lesson to be gleaned here, of course. That is, any effort to pinpoint the market's every high and low is not only maddening, but will likely be unsuccessful. It may even prove detrimental to your portfolio's value.

See, try as we might, the average person's (not to mention the average professional's) talent for spotting the broad market's peaks and troughs is pretty poor. We tend to get greedy only after big rallies we should have bought into months ago, often realizing too late that stocks were poised to pull back right after we got on. Likewise, we often hold onto poorly performing stocks too long on hopes for a rebound, only bailing out after steep sell-offs that are nearly ready to reverse course. Not too many investors like to go shopping in the middle of a bear market, either.

Warren Buffett is 100% correct, though -- when everyone else is finally selling due to a sweeping panic, you should be buying.

This assumes you're buying with a five-year mindset, of course. If you're only looking five months down the road, there's a reasonably good chance stocks could be priced lower then than they are now.