DNA Day is a holiday celebrated on April 25 commemorating the day in 1953 when James Watson, Francis Crick, Maurice Wilkins, Rosalind Franklin (all Brits except Watson who is from the US) and colleagues published papers in the journal Nature on the structure of DNA.
Additionally, on that day in 2003 it was declared that the Human Genome Project was very close to complete, and “the remaining tiny gaps [we]re considered too costly to fill.”
This diagram is was created by Madeleine Price Ball as part of her work for or with the United States government and is in the public domain. The image is widely distributed but wrong (says Wikimedia.)
DNA is synthesized only in 5′->3′ direction. Therefore only the leading strand is synthesized continuously. The other one, the lagging strand, is synthesized in several Okazaki-Fragments but not continuously as shown here. That’s the trouble with a good image; It over-simplifies the truth.