No one can perfectly time the market. However, the reality is that there are some times that are better to buy certain stocks and other times that aren't so great.

Now appears to be a great time to buy three healthcare stocks, in particular: Gilead Sciences (NASDAQ:GILD), Illumina (NASDAQ:ILMN), and Mylan (NASDAQ:MYL). I suspect if you wait much longer, these stocks won't be nearly as solid buys as they are currently. Here's why.

Two men holding buy and sell signs

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Gilead Sciences: Something is about to happen

Gilead Sciences stock currently trades at only seven times trailing-12-month earnings and under nine times expected forward earnings. Those multiples would look even better with the biotech's big cash stockpile factored into the equation. 

Some might say Gilead is a lost cause because of declining sales with its hepatitis C virus (HCV) franchise. I think that's a myopic view. My prediction is that Gilead will shake things up in the not-too-distant future with some sizable acquisitions. 

I don't have to be Nostradamus to be right. Gilead's executives have clearly stated that they're looking to make one or more deals. The company has spoken with ratings agencies about debt leverage for supporting acquisitions. That doesn't imply small deals are in the works.

As for timing, Gilead Sciences CEO John Milligan recently said the company is looking for a catalyst this year. There are several potential deals the biotech could make that would probably excite investors again and rejuvenate the stock. Something is about to happen with Gilead. Now is the time to buy the stock to profit the most when that something occurs.

Mylan: Simply worth more

Mylan stock took a big hit last year after receiving a lot of negative publicity related to the company jacking up prices for its EpiPen auto-injectors. Although shares have come back somewhat, the drug stock is still trading at less than eight times expected forward earnings. Mylan is simply worth more than that, in my opinion.

I'm not the only person who apparently thinks that Mylan should go higher. Billionaire David Tepper's hedge fund, Appaloosa Management, bought $125 million worth of Mylan's shares in the fourth quarter of 2016. 

There are several reasons why Mylan is attractive. First, don't worry about the EpiPen hoopla. The auto-injector will account for maybe 6% of the company's total revenue this year -- and not all of that in the U.S,. where Mylan was embroiled in controversy. 

More important, Mylan is poised to increase revenue and earnings over the next few years. Biosimilars will play a key role in helping drive that growth. The company could also make more smaller acquisitions to achieve additional growth. The stock could fluctuate up and down somewhat over the short run (especially if the company reports disappointing fourth-quarter earnings results), but I think Mylan is a smart long-term pick.

Illumina: New technology poised to dominate

Illumina is another healthcare stock that took a beating in 2016 but is mounting a comeback. The company reported better-than-expected fourth-quarter results, which certainly helped. Even better, though, was Illumina's announcement of its newest genomic-sequencing system, NovaSeq.

Customers have given rave reviews for NovaSeq. Illumina expects most of its customers who currently use the company's HiSeq high-throughput sequencing systems will convert to NovaSeq over the next few years. That means increased system sales for the company are on the way.

Don't be surprised to see Illumina's results in the next quarter or two negatively affected by the launch of the new system. It's likely that many customers will delay their purchases until they can get their hands on NovaSeq. Over the long run, though, this new technology should be a big win for Illumina.

Unlike Gilead Sciences and Mylan, Illumina's shares aren't priced inexpensively. The stock currently trades at 52 times trailing-12-month earnings and at 37 times projected forward earnings. Those seemingly nosebleed multiples aren't unusual for Illumina, though, and are actually on the low end of where the stock has traded in the past. 

The clock is ticking

I don't expect any of these three stocks to remain as attractive as they currently are for too much longer. Which is the best bargain? My pick would be Gilead Sciences.

Gilead's cash flow remains impressive even with lower HCV franchise sales. I won't be shocked if the big biotech winds up making several significant acquisitions this year and in 2018. The clock is ticking to grab Gilead's shares at current dirt-cheap prices. 

Keith Speights owns shares of Gilead Sciences. The Motley Fool owns shares of and recommends Gilead Sciences and Illumina. The Motley Fool recommends Mylan. The Motley Fool has a disclosure policy.