The 65th birthday of Aung San Suu Kyi, Burma's detained opposition leader, is being recognised by supporters both at home and abroad.
UN Secretary General Ban Ki-moon, US President Barack Obama and the UK have marked the occasion by reiterating calls for the Nobel laureate's release.
Members of Ms Suu Kyi's National League for Democracy plan to plant about 20,000 saplings around Burma.
Ms Suu Kyi has spent most of the last two decades in some form of detention.
Awarded the Nobel Peace Prize in 1991, she is one of the world's best known political prisoners, and is currently under house arrest in Burma's former capital, Rangoon.
Demonstrations calling for her release are planned around the world later on Saturday.
UN Secretary General Ban Ki-moon said he was "deeply concerned" that Ms Suu Kyi was still under house arrest.
"I have been persistently, consistently demanding that all the political prisoners including Daw Aung San Suu Kyi should be released without condition as soon as possible, so that they would be able to participate in the political process," he said.
The UK has also called for her immediate and unconditional release.
"Her continued detention, and that of more than 2,100 other political prisoners in Burma, contravenes international human rights law," said Foreign Secretary William Hague.
US President Barack Obama also joined the calls, referring to her as the "world's only imprisoned Nobel Peace laureate".
Activists in the US are planning to stage a rally in Washington on Saturday.
The Free Burma coalition staged a demonstration outside the Burmese embassy in Manila, in the Philippines, on Friday.
And a group of global statesmen called The Elders, founded by Nelson Mandela, left a seat symbolically empty for her at a meeting in South Africa on Thursday.
Messages of support from around the world have also been posted on Facebook and other social networking websites.
Supporters in the Burmese city of Rangoon say they plan to throw a small party for her at one of their houses.
The National League for Democracy won Burma's last elections in 1990 but was not allowed to take power.
The party has been forcibly disbanded, and Ms Suu Kyi has been banned from standing in elections later this year.