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The Facebook COO wrote an emotional tribute on her Facebook page to mark the day, which also fell on Rosh Hashanah, the Jewish New Year. Sandberg's husband, Dave Goldberg, died suddenly last year after sustaining a head injury on vacation in Mexico.
Goldberg was the CEO of SurveyMonkey and had a long career in the Silicon Valley tech scene. Goldberg and Sandberg have two children and were married for 11 years.
Here's Sandberg's post in full:
More than 1,000 people commented on the post, offering sympathy or sharing memories of Goldberg.
Facebook CEO Mark Zuckerberg also commented, saying: "It is fitting that today begins Rosh Hashanah. Dave helped so many people and made the world a better place for all us, and he would be proud of everything you are doing today."