The Old New Thing

A question about the FileTimeToLocalFileTime function turned out to be something else

March 6, 2015 Mar 6, 2015 03/6/15

Raymond Chen

Negative time.

Converting from a UTC-based SYSTEMTIME directly to a local-time-based SYSTEMTIME

March 7, 2014 Mar 7, 2014 03/7/14

Raymond Chen

Last year, I presented this commutative diagram A 2-by-2 grid of boxes. The top row is labeled FILE­TIME; the bottom row is labeled SYSTEM­TIME. The first column is labeled UTC; the second column is labeled Local. The upper left box is labeled Get­System­Time­As­File­Time. There is an outgoing arrow ...

On the various ways of getting the current time and date in Win32

November 1, 2013 Nov 1, 2013 11/1/13

Raymond Chen

There are a number of functions in Win32 that obtain the current date and time. Here's how they fit together: The starting point is . This returns the current time in UTC in the form of a structure. This also happens to be the time format used internally by the system, so this value can be retrieved with a minimum of fuss. You can also ...

How do I parse a string into a FILETIME?

November 2, 2012 Nov 2, 2012 11/2/12

Raymond Chen

Public Service Announcement: Daylight Saving Time ends in most parts of the United States this weekend. Other parts of the world may change on a different day from the United States. The NLS functions in Win32 provide functions to convert a into a string, but it does not provide any functions to perform the reverse conversion. Here are ...

How do I generate a unique 32-bit value for a time zone?

November 4, 2011 Nov 4, 2011 11/4/11

Raymond Chen

Public Service Announcement: Daylight Saving Time ends in most parts of the United States this weekend. Other parts of the world may change on a different day from the United States. A customer asked the following question: Given two structures, I would like to compute a for each that I can then compare to determine whether they ...

Why does my TIME_ZONE_INFORMATION have the wrong DST cutover date?

March 11, 2011 Mar 11, 2011 03/11/11

Raymond Chen

Public Service Announcement: Daylight Saving Time begins in most parts of the United States this weekend. Other parts of the world may change on a different day from the United States. A customer reported that they were getting incorrect values from the function. I have a program that calls , and it looks like it's returning incorrect DST ...