Today is as good a day as any other.
Prince Siddhartha Gautama, who’d one day meditate under a Bodhi tree until he reached enlightenment and became the first Buddha, was born on this day in 564 BCE, only not really. It could have been as much as 150 years prior. Various traditions add different characters and drama to the circumstances of his birth. Nobody can agree on where he was born, either. Was it India or Nepal? The official celebration of Buddha’s “birthday” — called Vesakha — wasn’t formalized until the first World Fellowship of Buddhists met in 1950 and agreed to it. Different countries can still opt to call the day something different and celebrate it on different dates.
Nobody knows if Jesus was born on December 25; in fact, it’s pretty certain that he wasn’t, since it’s also the date for the pagan festival “Sol Invictus” and wasn’t applied to Jesus’s birth until the newly-founded Church in Rome was busy codifying the books of the Bible and its official structures in the 4th century CE. Muhammad was born in 570 CE, give or take a couple of years, and tradition defines the particulars of the event, not eyewitness historical reporting. This isn’t just a religious thing. Tradition also defines when the British celebrate their king or queen’s “official” birthday (only coincidence might make it the same as the real dates, which in this case are known), and shared desires for three-day holiday weekends tell Americans when to commemorate George Washington’s birthday. Most famous inventions can be traced back to a founding moment, whether it was truly the time or place that gave birth to them.
Communities have always been more important than facts when determining truth.