Deno: Deno.utime() errors when supplied date parameter

[cknight]

Given the following code:

await Deno.utime("my_file.txt", new Date(), new Date());

The process errors out on v0.38.0 with:

error: Uncaught InvalidData: invalid type: floating point 1585688574.996, expected u64

The same error is present with Deno.utimeSync() as well.

[parkerdgabel]

I'm looking to contribute. I'll take a look at it.