The word "declared" is correct and usable in written English. It is usually used in the past tense to mean "announced officially". For example, "The president declared a national holiday to celebrate the country's independence.".
Kosovo declared independence from Serbia in 2008.
Gray was chased and subjected to an arrest declared unlawful by the city's top prosecutor.
The accountant's fees were fully declared for tax purposes and he paid tax on the benefit.
"We have been the UK's favourite coffee shop for some time; we remain the taxman's favourite coffee shop too," declared Andy Harrison, chief executive of parent company Whitbread.
"Four days after Germany declared war, they arrived in Tczew.
Lawyers for the two men appeared in the federal court in Sydney on Friday seeking to have the notices declared invalid and cancelled.
He declared himself delighted with his preparations, and this performance was a vast improvement on his dismal defeat by Lleyton Hewitt at Queen's last week.
I love the desktop app, it’s always running on my Mac. Ludwig is the best English buddy, it answers my 100 queries per day and stays cool.
Cristina Valenza
Retail Lead Linguist @ Apple Inc.