Idiomatic usage: dated at vs. dated to

Most of the time

dated at denotes a time period. (dated at + number of years)

dated to is followed by a date. (dated to + date)

Incorrect: Rock samples taken from the remains of an asteroid about twice the size of the 6-mile-wide asteroid that eradicated the dinosaurs have been dated to be 3.47 billion years old and thus are evidence of the earliest known asteroid impact on Earth. 

Correct: Rock samples taken from the remains of an asteroid about twice the size of the 6-mile-wide asteroid that eradicated the dinosaurs have been dated at 3.47 billion years old and thus are evidence of the earliest known asteroid impact on Earth.

Note: dated to be is unidiomatic