Why do File.GetLastWriteTimeUtc and FileInfo.LastWriteTime return different values for GMT?

Question

So I have a file..

var myFile = C:\docs\MyFile.pptx

and when I noticed that

FileInfo fi = new FileInfo(myfile);
var lastModified = fi.LastWriteTime;

and

var lastModified = File.GetLastWriteTimeUtc(myFile);

are returning different values. Why is this? The FileInfo value corresponds to the one displayed in Windows Explorer Date Modified column. Why do they differ? I would have expected them to would return exactly the same value.

What is your local timezone? `FileInfo.LastWriteTime` is probably returning a localized value. — Guvante, Mar 09 '15 at 17:28
Your question title says different but your code is different — Ehsan Sajjad, Mar 09 '15 at 17:31
What's the difference between them? This info might help others to provide a useful answer. — Florian Greinacher, Mar 09 '15 at 17:32
And where does GMT come in? What values are you seeing? Your question is very unclear at the moment (especially with the first line of code, which wouldn't compile...) — Jon Skeet, Mar 09 '15 at 17:32

score 2 · Accepted Answer · answered Mar 09 '15 at 18:04

2

I've actually checked the code in Reflector and they both do the exact same thing, i.e:

return DateTime.FromFileTimeUtc((long) data.ftLastWriteTimeHigh << 32 | (long) data.ftLastWriteTimeLow);

vs

return DateTime.FromFileTimeUtc((long) this._data.ftLastWriteTimeHigh << 32 | (long) this._data.ftLastWriteTimeLow);

I've also tested it and dates are the same. You must have accidentally compared Utc with a non-Utc function.

answered Mar 09 '15 at 18:04

bokibeg

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That's exactly what I did. – JKennedy Mar 10 '15 at 16:50

Why do File.GetLastWriteTimeUtc and FileInfo.LastWriteTime return different values for GMT?

1 Answers1