[fpc-devel] Problem with Now() and time changed by ntpd

[Sven Barth]

On 01.11.2011 14:03, Henry Vermaak wrote:
> Also, how cheap is this on Windows? Presumably they will also have to
> deal with potential system services running while updates fix daylight
> saving time changes? If they don't use shared memory for this, I'd wager
> that it's just as slow as libc localtime.

I've checked the Windows implementation. FPC's RTL in the end calls the 
function GetLocalTime which - as the name suggests - already returns the 
time that belongs to the current timezone (and DST settings). The 
implementation of that is cheap as well: the current bias from UTC is 
located in a shared memory section which the kernel maps into each 
running process. Thus only that one location (and the location were this 
setting is saved) is changed if a change of the timezone or the DST 
happens. So this is very cheap.

Note: for this I've looked into the source of ReactOS.

Regards,
Sven