This March conveniently marks both the one-year anniversary of the stock market trough during the Great Recession and the ten-year anniversary of the dot.com bubble peak. As such, the trailing 1-year and 10-year performance readings of all mutual funds just had a facelift.

Morningstar gives us a timely reminder:

For the trailing 12 months:

A look at the one-year returns for all of Morningstar's fund categories shows how incredibly strong, and also remarkably broad, the rally has been. The category returns should make one realize how unlikely it is that such performance will recur on more than the rarest occasions.

..., it's always tough to predict the markets, but I'd guess that investors should not assume they'll be getting returns of this magnitude every year. With that in mind, perhaps the best approach right now might be to smile, take a moment to be grateful for such gains, and then forget that the past 12 months ever happened.

For the past ten years:

This month also marks the 10-year anniversary of the market top reached after the Internet-fueled bull market. (Or, if you prefer, it marks the start of the dot-com crash and subsequent bear market.)

That means many funds' 10-year returns look much different now than they did a year ago--or even more to the point, two or three years ago--when the bulk of the stunning late-'90s growth rally was still being included in those 10-year returns and rankings. I wrote about this phenomenon in November 2009 when the changes in rankings had already begun but had yet to take full effect. Now the numbers from the rally of the late 1990s and early 2000 have completely vanished from all funds' 10-year records.

As a result, the records of value funds have received quite a boost, for all of their lagging in the late '90s has disappeared from their 10-year records. Conversely, growth-oriented funds have lost their glory years. ... Make sure to keep this phenomenon in mind when you look at 10-year returns and rankings from this point onward.