You can use TzSpecificLocalTimeToSystemTime and SystemTimeToTzSpecificLocalTime from kernel32.

Raymond Chen discusses the issue here: Why Daylight Savings Time is nonintuitive. And that's just considering times in the future. Do not expect the attempt to account for daylight savings at the time being converted to be 100% accurate. This class appears to be (loosely) modelled on the. In the other direction use ToUniversalTime. The code becomes: LocalDateTime := (UniversalDateTime) The DateUtils.TTimeZone type, introduced in XE, attempts to do just that.

Note that this conversion treats daylight saving as it is now rather than as it is/was at the time being converted. It should be obvious how to reverse this. File time -> local file time (this is the conversion from UTC to local).Result := UTCDateTime // Default to UTC if any conversion function fails.Īs you can see the function transforms the UTC date time as follows: Result := SystemTimeToDateTime(LocalSystemTime) If FileTimeToLocalFileTime(UTCFileTime, LocalFileTime)Īnd FileTimeToSystemTime(LocalFileTime, LocalSystemTime) then begin SystemTimeToFileTime(UTCSystemTime, UTCFileTime) function LocalDateTimeFromUTCDateTime(const UTCDateTime: TDateTime): TDateTime ĭateTimeToSystemTime(UTCDateTime, UTCSystemTime)

This is the function that I use to convert from UTC to local.

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