HAVANA, Cuba - Cuban revolutionary leader Fidel Castro has made it to 90, with the melody of "Happy Birthday" ringing out at midnight across Havana's seafront drive where thousands of Habaneros were celebrating on the first night of the city's annual carnival.

Castro's birthday, normally marked in a low-key fashion (Castro was fond of spending at least part of the day sharing a cake with young children), has dominated the local media increasingly since June. Ironically, for a man who opposed the cult of personality and statues in his honor, numerous photo exhibits and documentaries have been rolled out as tributes to what many Cubans see as the iconic rebel's positive contributions to their country, from fomenting culture, such as the National Ballet, to free universal health care and education.

What might be described as a massive class in Cuban history has been running nonstop on state-run television and dominating the 30-minute national nightly newscast. Only the Olympics have garnered as much attention in the past week.

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Having survived numerous assassination attempts, not to mention the serious intestinal illness and botched operation that eventually forced his retirement from public life, most Cubans feel Fidel Castro has earned the right to celebrate reaching 90.

He remains enormously popular, especially among older Cubans who are quick to say that while they might not agree with all his ideas, he has done much to improve their lives and put Cuba on the map as an international player of a magnitude that far outreaches its size as an island.

But Castro reaches 90 at a time when Cuban society is in the process of change, transitioning in ways anathema to many of the ideas of the man who for more than five decades set the political discourse on what life should be like on the largest of the Caribbean islands.

Castro fully passed the baton to his younger brother Raul in 2008 and since then Raul has slowly implemented a series of economic and political changes unimaginable under his predecessor. Not least of which is reestablishing diplomatic relations with Cuba's arch-enemy, the United States, and hosting the first visit by a sitting U.S. president to Cuba in nearly a century -- a visit that Fidel Castro would lambast in an editorial criticizing Barack Obama's speech to the Cubans as more of the same regime change policy practiced by 10 U.S. Presidents.

But the elder Castro's world has changed in a more intimate way. The round-the-clock workaholic, constantly surrounded by people, weighing in on everything from disarmament to nutrition to approaching hurricanes, we are told, spends his time reading and writing at home. Only occasionally does he appear in public and receive high-level visitors. And a rainy day can get him down, as we learned from a TV interview with one of his biographers, a young woman who said Castro's wife welcomed her recently to his home by saying he was depressed by the gray day and that her visit would cheer him up.

Society outside his doors has changed too and is changing more. His vision of a government that offers full employment for all, a guaranteed living wage, and a focus on the good of all has also been eroded. Officially some 500,000 people are now private entrepreneurs or work for them but the figure is likely much higher if you count those working without permits and public workers who moonlight. University graduates who once hung their diplomas on the wall and moved straight into assigned employment in the state sector are now either not being offered a state job or are rejecting the low salaries that go with them and opting for the private sector, black market or migration. Many begin their departure by applying for graduate degree programs in Europe or the United States.

The generation that has grown up since 2006, when Castro first fell ill, does not remember the vital, charismatic figure once omnipresent on television and at public events. They are more interested in the reforms begun by Raul Castro - more freedom to travel abroad, more choice of employment, access to internet, more independence of action. And even the most revolutionary of parents, many of whom consecrated their lives to secure Fidel's dreams, find their thinking shifting as they support their children's desires for a life different than theirs, a life without the sacrifices and with more material rewards. And to a great extent the new generation is apolitical. They're more interested in Facebook and IMO than the news as can be seen at any of the island's public Wi-Fi hot spots.

The economic opening taking place has created more class and racial differences than existed in the world envisioned by Castro, but he is surely aware that the gap between haves and have nots dates back to the 90s when Cuba's socialist allies and main trading partners collapsed, leaving the island bereft of hefty subsidies that supported a rising lifestyle and expectations among Cubans.

He also watched the rise and current fall of Latin American allies, populist leftists such as Hugo Chavez, who was his protégé and whose death was an enormous blow.

Still we don't know exactly what Fidel Castro is thinking about how his world has changed as he marks his 90th birthday today. He has wisely refrained from voicing his opinions on the reforms being implemented and in doing so helped Cuba make a smooth transition from his era to that of Raul Castro and a younger generation of leaders. And that leadership insists that Fidel Castro's ideas are still the guiding principles of the changes taking place, although some critics suggest it's the retired leader's views that conservatives are using to slow the pace of reforms.

One thing that hasn't changed: Fidel Castro is a man of surprises and no one yet knows if he will make a public appearance on this historic birthday. Strong rumors in the street say he will, most likely at Saturday night's performance by a Fidel-backed children's theater group in Havana's largest theater, the Karl Marx.