Events to celebrate the Welsh patron saint St David have taken place across Wales and the world.
Cardiff staged the sixth national annual 1 March parade, another march in Wrexham, and a fun run in Aberystwyth.
A world record was claimed as free entry to the National Botanic Garden of Wales near Carmarthen saw hundreds turn up in traditional Welsh dress.
London mayor Boris Johnson has sent St David's Day greetings and is flying the Welsh flag over City Hall for two days.
The botanic garden would normally be happy to see 300 visitors on a Sunday in March, but estimated the turn-out at at least 2,500 for St David's Day.
"We set out to host a world record for the greatest number of people dressed in Welsh costume gathered in one place," said David Hardy, spokesman for the garden at Llanarthne.
"In fact we were told there is no such record at the moment so what we've done today is actually the benchmark for the future.
"It's a question of 'beat that if you can' because we set the record today," he said.
"Estimates are that we had 201 people gathered for the world record attempt but it has not been made official yet."
He said the day had been "a tremendous success for the garden with 2,500 visitors and counting as we speak."
Despite the free entry many people donated cash as they arrived at the garden and its food outlets were overwhelmed with business.
Pensioner Jean Peace, of Pontyates, Carmarthenshire, was one of many adults to take part in the world record attempt.
"I think it was a fantastic idea and hopefully an event like this will convince people to visit the garden more often."
Elsewhere, Boris Johnson sent St David's Day wishes.
The London mayor can boast some Welsh connections, having stood unsuccessfully in 1997 as a Conservative parliamentary candidate in Clwyd South, and has Welsh former BBC reporter Guto Harri as his director of communications.
The mayor said: "Happy St David's Day to all of you.
Mark and Leo Lewis joined the Welsh Lady Run on Aberystwyth promenade
"It's with great pleasure that I can tell you that the red dragon will be hoisted over City Hall this Sunday and fly for two days as a tribute to your patron saint, Wales as a nation and the Welsh community in London which is one of the most ancient, creative and appreciated.
"Enjoy the celebrations."
All monuments managed by Welsh heritage organisation Cadw offered free entry to the public for the day.
London already had a taste of Wales earlier in the week with a Welsh foods festival held in Oxford Street on Friday, while First Minister Rhodri Morgan hosted a reception in Brussels the day before.
Heritage Minister Alun Ffred Jones has already launched a collection of stamps, called Celebrating Wales, with one featuring a picture of St David.
In Cardiff, there was live music from midday outside the National Museum Wales before the St David's Day parade en route to the Senedd building in Cardiff Bay.
Traditional Welsh music was on offer inside Cardiff Castle, with free entry to the castle grounds.
Wrexham held its own parade for the first time, and a St David's Day fancy dress fun run took place in Aberystwyth, including celebrity runner BB Aled from Radio 1.
Chester Zoo offered free entry to anyone named David (first name or surname) who comes with a paying customer to mark the saint's day.
On the other side of the world, the New Zealand capital Wellington was the first in the world to mark this year's St David's Day and hosted a flag-raising ceremony at the British High Commission at 0900 local time.
The USA held its sixth annual Wales Week USA, with a performance from Welsh pianist Llyr Williams ahead of his Carnegie Hall debut, Welsh dishes at a New York restaurant and discussions of their work by authors Owen Sheers and Paul Watkins at New York Public Library.
In Chicago, the iconic Wrigley Building was lit up on St David's Day evening in the red, green and white of the Welsh flag, while Sir Tom Jones will perform in concert in Boston.
In San Francisco, the Welsh-born British Consul General Julian Evans hosted a reception while in Los Angeles, another event for the creative industries was staged by International Business Wales with the UK Film Council.
Events also took place in Chonquing, China, including interactive workshops by Techniquest Wales and a visual arts exhibition.