Question

I noticed that no matter what I do, tofiletimeutc() always returns the same as toFileTime(). I need to produce a UTC timestamp. So I tried this experiment in Powershell:

(get-date).tofiletime();
(get-date).touniversalTime().tofiletimeutc();
(get-date).tofiletimeutc();

and the output is:

129757574870723241
129757574870723241
129757574870723241

(All 3 are identical, local-time stamps. Time zone is set to Pacific).

(get-date).touniversalTime() works as expected, but no matter which “to-utc” function I use, it is for some reason converted back into local time. Does anyone see what is going on?

Answer 1

Yes, it does work all three values you see are filetimes “in UTC”.

Background:

The Windows FILETIME is defined as: “a 64-bit value representing the number of 100-nanosecond intervals since January 1, 1601 (UTC).”

Both DateTime.ToFileTime() and DateTime.ToFileTimeUtc() return a UTC-based value.
In fact, DateTime.ToFileTime() is implemented as DateTime.ToUniversalTime().ToFileTimeUtc().

Update Concerning the comments:

The value is always the same, as said above, what you “see” when converting it back to a DateTime instance and dumping that, on which method you use:

Those two return the “same” DateTime value with DateTimeKind.Utc and the DateTime value “adjusted” to UTC.

[datetime]::FromFileTimeUtc((get-date).ToFileTime())
[datetime]::FromFileTimeUtc((get-date).ToFileTimeUtc())

Those two return the “same” DateTime value with DateTimeKind.Local and the DateTime value adjusted to local.

[datetime]::FromFileTime((get-date).ToFileTime())
[datetime]::FromFileTime((get-date).ToFileTimeUtc())