Function unix_seconds_and_nanos 

pub fn unix_seconds_and_nanos(time: SystemTime) -> (i64, u32)

A time as coven_user_files lists a modification time, in modified_seconds and modified_nanos: whole seconds since the Unix epoch, rounded down, and the nanoseconds past that second, from 0 through 999,999,999 (§17.3). Half a second before the epoch is (-1, 500,000,000). An app compares a file’s time on disk with the view’s through it.