Fidel Castro is marking his 87th birthday behind closed doors, with tributes in official media serving as a reminder of his outsize influence on Cuban history.

The date also underscores that the clock is ticking on his generation's grip on power, with Cubans increasingly obliged to contemplate a post-Castro future.

Havana mechanic Dayren Silva said Tuesday the occasionally released photos and videos of the retired leader make him realize that "the calendar is irreversible."

Raul Castro has been in power since a near-fatal illness forced Fidel to step aside in 2006.

He says his current term ending in 2018 will be his last, concluding nearly six decades of rule by the brothers.

In February Raul Castro named Miguel Diaz-Canel, 53, as his chief deputy and heir apparent.