date_trunc_y
Truncates a calendar date at the year threshold
Examples:
date_trunc_y(to_fixed_timestamp('2017-12-13T00:24:53Z'))
-- Result: "2017-01-01T00:00:00Z"
date_trunc_y(to_floating_timestamp('2017-12-13T00:24:53Z'))
-- Result: "2017-01-01T00:00:00"
date_trunc_y(to_fixed_timestamp('2017-12-31T23:24:53-0930'))
-- Result: "2018-01-01T00:00:00Z"
a -> a