The birds have been chirping for weeks now, and the last vestiges of winter are on their way out.

The days are getting longer. The spring-forward edition of Daylight Saving Time means the Sun shines later, and the tilt of the Earth mean the Sun shines longer.

The telltale signs of spring have long been in the air, despite what the erratic weather would rather we think, but the surest sign of all returned full force on Monday.

Baseball, of course, is back.

And with baseball’s return come perennial flowers, rolling thunderstorms, and a sense of optimism unabashed by the dog days of summer.

There are no days too hot to spend outside in the spring. There are no days when temperatures break 100 degrees, and there are no days, at least until July, where a team can be ruled out of the playoffs.

Baseball stretches the length of three calendar seasons, and with that length come new stories every week.

But the unpredictability makes baseball the great American pastime. Francisco Liriano, the Pittsburgh Pirate starting pitcher on opening day, hit the first RBI of the young season.

A pitcher hit the first RBI, not home-run champion Chris Davis of the Baltimore Orioles, not Nelson Cruz of Seattle, or Washington’s Bryce Harper.

The St. Louis Cardinals, at 0-1, are tied for the worst record in baseball.

And the Cubs, the lovable losers from the North Side, thanks to marquee free-agency additions and a core of young players barely scratching the surface of their talent, are the odds on favorite to win the World Series.

Yes, the Chicago Cubs. Pick your jaw up off the floor and buckle up, because the Cubs really have a chance this year. But that’s easy to say after one game.

That is the penultimate example of what this game is about. The unpredictability, and the relentless optimism that comes with it, make the first months of a season great.

Of course, baseball is not a perfect game. Players still use performance enhancing drugs, and Yankee fireball-throwing closer Aroldis Chapman, nicknamed the Cuban Missile, was suspended 30 games after an alleged domestic-violence incident.

Those real controversies are important and should not be taken lightly. These stories reignite where a player’s lack of character overrides his utility on a ball field.

But come spring, the story lines of the winter become off-season story lines.

The focus returns to on- field actions, rather than off, with fans living and breathing every detail of the three-hour, nine-inning chess match happening before their eyes.

Between Monday and the playoffs, each team will play 162 games, but as the season progresses past the spring, into those dog days, and into the cooler, shorter days of fall, those games will matter to fewer and fewer teams.

That’s what made Monday great. No team has been eliminated from the playoffs — even Milwaukee, despite a 12-3 clubbing by the San Francisco Giants.