When Is the Best Time to Buy Stocks? What 10 Years of Real Data Shows

Every investor asks some version of this question eventually: is there actually a best time to buy stocks, or is that just something people say after the fact when a trade works out? It's a fair question, and it has a real answer — just not the one most people expect. We pulled 10 years of S&P 500 data and ran the numbers ourselves rather than repeating the usual talking points.

The short version: timing matters far less than staying invested, seasonal patterns are real but small, and the highest-leverage thing you can actually control is having a pre-defined price in mind and a way to act on it — not a feeling about whether "now" is the right moment.

Time in the Market vs. Timing the Market

This is the single most tested question in market-timing research, and it isn't close. Missing a small number of the market's best days does outsized damage to long-term returns, because those days tend to produce a disproportionate share of total gains — and they cluster near the market's worst days, not far away from them.

We tested this ourselves using 10 years of SPY (S&P 500 ETF) daily closing prices, January 2016 through December 2025 — 2,514 trading days:

Ten days, out of 2,514 — roughly 0.4% of trading days — cut the decade's return nearly in half. Thirty missed days, less than 1.2% of the period, erased the entire gain.

Lump Sum vs. Dollar-Cost Averaging

If you already have cash to invest, should you put it all in at once, or spread it out over several months? The historical evidence leans toward investing it immediately: because markets rise more often than they fall over any long stretch, holding cash on the sidelines while you dollar-cost average in has a real opportunity cost on average. Vanguard's well-known study of rolling 10-year periods in the US market found that a lump-sum investment outperformed a dollar-cost-averaged approach roughly two-thirds of the time.

That statistic doesn't make dollar-cost averaging wrong — it makes it a trade-off. Spreading an investment out over months reduces the risk of investing everything right before a sharp drop (the 2000 and 2007 market peaks are the textbook examples of when DCA would have meaningfully outperformed), and it removes the emotional weight of picking a single entry point. For money you're investing gradually anyway — a portion of every paycheck — dollar-cost averaging isn't really a choice at all; it's simply how most people invest by default, and it works well over time regardless of the lump-sum comparison.

Seasonal Patterns: What the Calendar Actually Shows

Stock market seasonality gets repeated so often it's easy to assume it's folklore. Using the same 10 years of SPY data, we calculated the average return for every calendar month:

A few patterns worth noting line up with the folklore:

• "Sell in May" has some real basis — the May-through-October stretch averaged noticeably weaker returns than November-through-April in this sample, though far from every individual year followed the pattern.
• September really was the weakest month, on average, over this decade — consistent with its long-standing reputation as the market's worst calendar month.
• November was the strongest month by a wide margin, and combined with a positive December, supports the "Santa Claus rally" idea of a favorable late-year stretch.
• The January effect is visible but modest — January's average return was solidly positive but well behind November and July.

There's also a shorter-horizon pattern worth knowing: research on the two weeks leading into scheduled Federal Reserve meetings has documented a modest but persistent upward drift in equity prices during that window, sometimes called the pre-FOMC drift — one more data point suggesting the calendar carries some real information, in small doses.

Intraday Timing: When During the Day to Place Orders

Zooming from months down to minutes, the pattern is even more mechanical. The first 30 minutes after the 9:30am ET open and the last 30 minutes before the 4:00pm ET close consistently carry the session's highest trading volume and volatility — the open reflects overnight news and pre-market positioning getting digested all at once, and the close reflects funds and algorithms squaring up positions for the day.

What that means practically: if you're placing a market order and want reliable execution, that extra liquidity can work in your favor. If you're placing a limit order at a specific price, the calmer middle of the session often gives you a steadier, less noisy read on whether your price is actually being reached versus getting caught in an opening or closing swing that reverses within minutes.

Timing Individual Stocks: Pullback vs. Chase

Everything above is about the market as a whole. Timing an individual stock is a related but separate question, and the evidence-backed approach looks different: rather than trying to predict a top or bottom, the better setup is buying a brief, orderly pullback within a confirmed uptrend rather than chasing a stock that's already extended well above its recent range.

The hard part is telling a constructive pullback apart from a stock that's actually breaking down — they can look identical for the first day or two. A few things that lean constructive: the pullback stays shallow relative to the prior move, volume dries up on the way down (sellers aren't in a hurry) rather than expanding, and the stock holds above a level that mattered before — a prior breakout point, a rising moving average, a level that previously acted as resistance and should now act as support. A pullback that breaks below that level on heavy volume is a different animal entirely, and chasing a bounce there is a much lower-probability bet.

Valuation-Adjusted Timing

The same business isn't the same investment at every price. A stock trading at 25x forward earnings and one trading at 40x forward earnings on the same growth story carry very different risk profiles, even if the momentum looks identical on a chart — the higher multiple is pricing in more of the good news already, which means less room for error if results disappoint. Checking where a stock's current valuation sits relative to its own history and its sector, not just whether the chart looks strong, is part of the timing decision that's easy to skip when a stock is moving fast.

It's also often better to wait for a catalyst to actually confirm a thesis than to buy early in anticipation of one. Buying ahead of an expected earnings beat, product launch, or macro shift means betting on both the outcome and the market's reaction to it — two separate things that can each go wrong independently. Waiting for confirmation gives up some of the move, but it also removes one of the two ways to be wrong.

The Practical Framework: Turn Timing Into a System

Everything above points to the same conclusion: the goal isn't to predict the perfect moment, it's to decide your entry criteria in advance — a specific price, a specific technical level, a specific confirmation — and then execute without hesitating or second-guessing once that condition is met. The two hardest parts of timing in practice are patience (waiting for your actual level instead of chasing) and attention (actually noticing the moment it happens).

That second part is where most manual timing plans quietly fail. A price alert set at the level where you've decided you want to buy — or the dollar-cost averaging schedule you've committed to — turns a plan you have to remember into one that finds you.

Common Mistakes

Treating seasonality as a trading signal instead of a mild tilt. September being the historically weakest month doesn't mean every September is down — it means the average leans slightly negative across a wide range of individual outcomes.

Waiting for a "better price" indefinitely. The data above shows the cost of even a handful of missed good days. An investor perpetually waiting for a lower entry that already happened tends to end up worse off than one who bought and simply stayed invested.

Confusing a pullback with a breakdown. Buying every dip without checking whether the trend and the level actually held is a different, much riskier bet than buying a confirmed constructive pullback.

Buying purely on momentum without checking valuation. A stock can be in a real uptrend and still be a worse risk/reward than it was a month earlier, if the price has moved faster than the fundamentals justifying it.

Having a plan but no way to execute it. Deciding on a target entry price is only half the system — without a way to be notified the moment it's reached, the plan depends on remembering to check at exactly the right time, which is where most timing plans actually break down.

The Bottom Line

There is a best time to buy stocks, but it isn't a month, a day of the week, or a time of day — those factors nudge the odds slightly, nothing more. The two things that actually move the needle are staying invested rather than trying to dodge the market's worst days (and risking the best ones along with them), and having pre-defined entry criteria you can act on the instant they're met, rather than a vague sense that "now feels right." Seasonality, intraday timing, and valuation context are all real, minor inputs to that plan — not substitutes for having one.

Related Reading

• Dollar-Cost Averaging: The Complete Guide
• Support and Resistance Levels Explained
• Stock Market Seasonality Guide
• How to Set Stock Price Alerts