The on-disk DateTime key shape: i64 LE UNIX seconds, then u32 LE subsecond nanos -- 12 bytes total, never a JS Date (which cannot hold nanosecond precision and cannot represent the sentinel year 9999 used by keyMax).
DateTime
i64 LE
u32 LE
Date
keyMax
The on-disk
DateTimekey shape:i64 LEUNIX seconds, thenu32 LEsubsecond nanos -- 12 bytes total, never a JSDate(which cannot hold nanosecond precision and cannot represent the sentinel year 9999 used bykeyMax).