The former member of staff at the Royal Mail had two parties, one at the residential home where she has lived since March, and a champagne supper in the presidential suite of the Grand Hotel in King Edward's Parade.
Her only sadness was that husband Owen, known as Bill to friends and neighbours at their former home in Beachlands, Pevensey, was not there, having died on his 95th birthday this year.
Joan and Bill moved to Eastbourne in 1977, shortly after marrying late in life, she at 61 and he at 57.
The couple, who knew each other for 25 years before marrying, had visited on holiday, fallen in love with the town and resolved to move here when they retired.
They swam in the sea every day after first moving and continued to walk along Pevensey Bay in their 90s and Bill mowed the lawns of the single women who lived near to them until he was 94.
Joan was born in Penge, near Croydon, and grew up in Reigate. She worked for the General Post Office telephone exchange and the Royal Mail all her working life.
She loves music and food and was known as the perfect hostess, always providing cakes and drinks.
Her nephew Robin Boss, one of the six nieces and nephews Joan, who did not have children of her own, looked after during World War II, came to both of her birthday parties,
Robin's partner, Jenny Sargent, said the centenarian had a great birthday and all the guests had remarked on how beautiful she looked.
She said, "She worked keeping the lines of communication going throughout World War II and she was a great help with her brother's six children for her sister-in-law while he was away in the RAF.
"She was regarded with so much affection by her nieces and nephews, like a second mum, and now, with these parties, she is getting back what she put in for them."